# Is incest among adopted siblings illegal?
**URL:** https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819
**Category:** Factual Questions
**Created:** [August 7, 2002, 6:56pm UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819 "2002-08-07T18:56:03Z")
**Posts on this page:** 20
**Page:** 2
### Author:  [@mazzer](https://boards.straightdope.com/u/mazzer)
#### Post date: [August 8, 2002, 2:45am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/21 "2002-08-08T02:45:00Z")
> [@](#):
>
> \*Originally posted by JRDelirious \*
> **OK, the OP does not ask if it’s right or wrong, but if it’s _illegal_. Almost everywhere, it is. As mentioned before, the straight factual answer depends on each jurisdiction’s laws.**
“It” is incest. But what is incest? Dictionary says: “Sexual relations between persons who are so closely related that their marriage is illegal or forbidden by custom” or “The statutory crime of sexual relations with such a near relative.”
Is this what we’re talking about? Or rather the _marriage_ of two siblings? Will someone for Cecil’s sake please clarify what they’re talking about?!
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### Author:  [@Squish](https://boards.straightdope.com/u/Squish)
#### Post date: [August 8, 2002, 3:36am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/22 "2002-08-08T03:36:01Z")
Sex between two consenting adults, blood relatives or not, with the exception of certain acts (sodomy, etc.) is not illegal, AFAIK. Marriage is something else.
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### Author:  [@TeaElle](https://boards.straightdope.com/u/TeaElle)
#### Post date: [August 8, 2002, 3:46am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/23 "2002-08-08T03:46:41Z")
It seems that affinity prohibitions would not apply if both partners were legal adults at the time of the affinity’s genesis. For instance, if I’m 30 and my mother is a 60 year old widow, and she marries a 60 year old widower with a 30 year old son, it seems strange that the law would prevent me from marrying that 30 year old son, especially since at that age it would be highly unlikely that we would’ve been raised in the same house or ever treated as siblings in anything more than a “get together on holidays and special occasions” sort of manner.
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### Author:  [@Paul\_in\_Qatar](https://boards.straightdope.com/u/Paul_in_Qatar)
#### Post date: [August 8, 2002, 4:05am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/24 "2002-08-08T04:05:32Z")
OK, what if the timing were reversed, I marry a thirty-year old woman and then Dad tries to marry her mother?
Would that be allowed in most states?
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### Author:  [@Nametag](https://boards.straightdope.com/u/Nametag)
#### Post date: [August 8, 2002, 4:18am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/25 "2002-08-08T04:18:57Z")
To recap my first post, most states no longer prohibit marriage between those related by affinity. However, I missed the fact that the OP really asks about sex, so I’ll answer this way: If marriage is OK, sex is OK.
Now, as to incest between blood siblings, many states have not gotten around to it at all; there is no federal law (that I can find) against incest between consenting adult siblings, but there are some states that have specifically banned it. (It’s hard to find facts about this because most laws and websites dealing with incest talk only about protecting minors)
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### Author:  [@GilaB](https://boards.straightdope.com/u/GilaB)
#### Post date: [August 8, 2002, 4:49am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/26 "2002-08-08T04:49:53Z")
> [@](#):
>
> \*Originally posted by slipster \*
> \*\*The last I heard, an uncle and neice or an aunt and nephew could marry in Rhode Island, but only if they are Quakers or Orthodox Jews. \*\*
[Nitpick mode]
According to Jewish law, an uncle can marry a niece, but an aunt can’t marry a nephew.
[/Nitpick mode]
(Not that any Jews that I know or have ever heard of have married their uncles/nieces. This is straight Biblical law, out of Leviticus 8:12-13.)
Knowing nothing useful on American laws on the subject, I’ll butt out now ;j .
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### Author:  [@chula](https://boards.straightdope.com/u/chula)
#### Post date: [August 8, 2002, 5:34am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/27 "2002-08-08T05:34:04Z")
> [@](#):
>
> \*Originally posted by Nametag \*
> \*\*Now, as to incest between blood siblings, many states have not gotten around to it at all; there is no federal law (that I can find) against incest between consenting adult siblings, but there are some states that have specifically banned it. (It’s hard to find facts about this because most laws and websites dealing with incest talk only about protecting minors) \*\*
This post is making things more confusing. Incest covers both marriage and sex, and it’s illegal between blood siblings in all states. (There’s no federal law because states generally deal with things like marriage.) From the Model Penal Code:
> [@](#):
>
> A person is guilty of incest, a felony of the third degree, if he knowingly marries or cohabits or has sexual intercourse with an ancestor or descendant, a brother or sister of the whole or half blood [or an uncle, aunt, nephew or niece of the whole blood]. “Cohabit” means to live together under the representation or appearance of being married. The relationships referred to herein include blood relationships without regard to legitimacy, and relationship of parent and child by adoption.
I’m not sure how many states follow the MPC with respect to siblings related by affinity only. I checked the first few states, and in Alabama it’s illegal, in Alaska no, Arizona no, Arkanas no, California no… I see a pattern forming.
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### Author:  [@papergirl](https://boards.straightdope.com/u/papergirl)
#### Post date: [August 8, 2002, 12:43pm UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/28 "2002-08-08T12:43:34Z")
My cousin in Florida married her stepbrother. They’d been step-siblings since grade school.
Then their parents divorced, so I guess techinically they aren’t step-spouses anymore.
Our family is a little odd.
~k
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### Author:  [@photopat](https://boards.straightdope.com/u/photopat)
#### Post date: [August 8, 2002, 3:15pm UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/29 "2002-08-08T15:15:55Z")
1. it impairs your ability to develop normal relationships with appropriate partners
I guess I’d have to wonder what constitutes an appropriate partner first. I mean, two non-related adults, regardless of the way they met would see to qualify. As to the legality, like the others have said, it depends on the state.
I personally don’t see anything wrong with it, although I will admit that had the two people grown up together as siblings since a very young age it would be a bit weirder than if their parents had married when they were teens or later.
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### Author:  [@scott\_evil](https://boards.straightdope.com/u/scott_evil)
#### Post date: [August 8, 2002, 3:34pm UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/30 "2002-08-08T15:34:40Z")
Then there’s the case of Debb Eaton, the first bootee on Survivor 2, who married her stepson after her husband/his father died.
I’d be more EW, but I feel sorry for her. I mean, she broke down on the reunion show and said going on the show was the worst mistake of her life. ☹
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### Author:  [@Guinastasia](https://boards.straightdope.com/u/Guinastasia)
#### Post date: [August 8, 2002, 8:12pm UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/31 "2002-08-08T20:12:37Z")
Um, nitpick-
_Doctor Zhivago_-Yuri and Tonya were NOT raised as brother and sister. Tonya’s family took Yuri in after his mother died-he was about 8 years old. They raised him as a son, but they were never really “brother-sister” to one another-just as friends who grew up together. They were sort of geared towards one another-it was always assumed that they would someday be married.
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### Author:  [@Muffin](https://boards.straightdope.com/u/Muffin)
#### Post date: [August 9, 2002, 1:22am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/32 "2002-08-09T01:22:19Z")
In Canada it probably would constitute criminal incest. Don’t know for certain, though. C.C.C. s. 155(4) on incest: "In this section, “brother” and “sister”, respectively, include half-brother and half-sister.
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### Author:  [@photopat](https://boards.straightdope.com/u/photopat)
#### Post date: [August 9, 2002, 1:41am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/33 "2002-08-09T01:41:05Z")
Well half-brother or half-sister, sure. I mean, they ARE relatives, since that means sharing either mother or father. Steps are different, because they aren’t actually related at all.
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### Author:  [@Muffin](https://boards.straightdope.com/u/Muffin)
#### Post date: [August 9, 2002, 1:53am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/34 "2002-08-09T01:53:01Z")
That’s what I’m not clear about.
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### Author:  [@Walloon](https://boards.straightdope.com/u/Walloon)
#### Post date: [August 9, 2002, 2:56am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/35 "2002-08-09T02:56:25Z")
> [@](#):
>
> \*Originally posted by stockton \*
> \*\*In response to the “EWWWWWW!” crowd, I have 2 words to send you scurrying back into your lairs:
>
> Woody. Allen.
Woody Allen dropped his girlfriend for his girlfriend’s adult daughter. Soon Yi Previn is the (adopted) daughter of Mia Farrow and Andre Previn.
Woody Allen and Mia Farrow were never married. Woody Allen and Mia Farrow never lived together.
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### Author:  [@susan](https://boards.straightdope.com/u/susan)
#### Post date: [August 9, 2002, 8:14am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/36 "2002-08-09T08:14:19Z")
“In love,” “sex,” “incest,” “marriage,” “consanguinity” etc. are not the same thing, as some of these posts have tried to elucidate.
Unless I missed something, these posts all assume the relationship is heterosexual. If it’s a same-sex relationship, consanguinity is not likely persuasive since they’re not going to have bio children together. Not allowing them to marry is irrelevant since the state won’t sanction their relationship anyway (other than VT, but let’s not muddy the waters). If they’re adults, and their state doesn’t have “sodomy/detestable acts against nature” laws, the question of il/legality based on their parents’ legal relationship (assuming there is one) still stands.
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### Author:  [@VDarlin](https://boards.straightdope.com/u/VDarlin)
#### Post date: [August 9, 2002, 11:57am UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/37 "2002-08-09T11:57:48Z")
Chalk Michigan up as a state that allows step-siblings to marry. I have a friend who married his step-sister there, and they now live here in California. They were both teens when their parents married, and were not raised together, even then, as he lived in CA, and she in MI, until he moved there a couple years after graduating high school. It’s kind of strange to think about, but I don’t see anything wrong with it. I personally don’t believe that it should be illegal for adopted siblings, so long as there is no blood link, but that does bring in the chances that the two were raised together as if they were blood related siblings.
Yes, my friend, and his family all joke about the fact that their family tree doesn’t fork(and that their son’s are also their nephews).
~V
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### Author:  [@Walloon](https://boards.straightdope.com/u/Walloon)
#### Post date: [August 9, 2002, 7:05pm UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/38 "2002-08-09T19:05:27Z")
The state of Wisconsin does not prohibit the marriage of step-siblings. On adopted siblings, the Wisconsin statutes are silent, although they do permit marriage between first cousins if one or both parties are sterile or past menopause. So apparently the guiding idea is genetic.
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### Author:  [@actionmanrandell](https://boards.straightdope.com/u/actionmanrandell)
#### Post date: [December 6, 2010, 9:10pm UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/39 "2010-12-06T21:10:56Z")
> [@chula](#):
>
> I don’t recall ever hearing anthropologists claim that there is a social reason such as you describe for the incest taboo. Most societies have pretty complex rules about who someone’s supposed to marry. The reason why close relatives are excluded is that inbreeding has dangerous biological consequences. Also, I heard an anthropology professor at UC Berkeley years ago make a convincing case that there is a genetic basis for the universal taboo against incest between siblings. Part of the support for this argument was the fact that people almost never mate with people they were raised with, even if they are not blood relatives. Based on his evidence, only someone who is severely disturbed or genetically defective would want to have sex with their adoptive sibling.
actually the danger isnt that much higher then a normal concenting person a normal couple have a bout a 2 to 3%chance of having a child who is born with congenital heart defect by the way that is the defect that the majority of family couples will have. a blood related couple have about a 7 to 8% chance of having a child with congenital heard defect but thats only people closely related for instance second cousins only have about a 3to4% chance of having that defect
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### Author:  [@actionmanrandell](https://boards.straightdope.com/u/actionmanrandell)
#### Post date: [December 6, 2010, 9:14pm UTC](https://boards.straightdope.com/t/is-incest-among-adopted-siblings-illegal/122819/40 "2010-12-06T21:14:36Z")
> [@Squish](#):
>
> Sex between two consenting adults, blood relatives or not, with the exception of certain acts (sodomy, etc.) is not illegal, AFAIK. Marriage is something else.
that is not true in almost every state in the united states sex with your brother or sister mother or father daughter aunt uncle nephew neice or 1st cousins is ilegal by punishment of up to 10 years in prison
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