Twins! What are the odds?

So, the littlest duckling has told us that she’s in the duckling way. It’s cool. She’s been married for a year as of this weekend, and she’s very healthy, and everybody’s thrilled about the whole thing. But here’s the deal. Momma-in-law has a twin sister. Fraternal, not identical, but we have twins in the family. Does that raise the odds of it continuing? Actual momma likes to spout off stuff like - it skips a generation. I don’t remember my pea-pod math, so I don’t know. But here’s the other deal. Momma-in-law and twin sister have two other sisters. Who are twins. So grandma-in-law and grandpa-in-law produced two separate set of twins. And there is the question. What are the chances that we have more than one egg in the basket?

Chances of a twin having twins is slightly more than for non-twins.

I recently learned that the incidence of identical twins is fairly constant in the human population, but the incidence of fraternal twins varies widely between different ethnic groups and regions.
There is a type of yam (IIRC) found in Africa that contains a chemical very similar to some fertility drugs, and the region that eats that yam has the highest incidence of fraternal twins on earth.

The stuff I’ve found ( http://www.twinstwice.com/twins.html for instance) suggests that identical twinning is not inherited.
That page suggest that a person who is a fraternal twin has a 1-in-17 chance of having fraternal twins, and if your mother was a fraternal twin that increases your chance of having fraternal twins (by an unspecified amount). Both of those seem to assume that the person in question is female, as it has to do with inheriting a tendency to … deploy two eggs at the same time.

So, while it probably isn’t a good idea to share any of this with your in-laws, the stuff I’ve found suggests that your son-in-law’s family history is irrelevant to your daughter’s chances of having twins.

Related question: Is it true that DNA evidence is useless against twin siblings in a court of law since they both have the same and there’s no way of telling which sibling it came from?

That was going to be my WAG. Fraternal twins depend on two eggs being released in a cycle, and therefore would be possible if dual-egg production is a heritable trait on the maternal line. In this case, the mother-in-law’s genes aren’t going to be relevant to egg production. However, if the expected baby (congrats!) is female, she might have an increased chance of being the mother of fraternal twins someday.

I actually checked this out once, for some reason, and at that time Lloyd’s of London was giving odds of – eh, I don’t know odds. One chance in 88. That was for either type of twins, fraternal or identical.

Here are some statistics from the UK - likely they are the same on your side of the pond:

Only if you can’t determine which one was where. The DNA can’t differentiate the two siblings but it still indicates one of them was there, now you need other information in order to determine which one.

Carrying multiples is often a high risk pregnancy, for mum and/or baby A/Baby B. The higher the multiples the more potential for risk.

One of my twins was born a little over 2 pounds and the other under 3. Both are healthy and my wish for you is that whatever is in your basket you and yours are healthy.

Be well

True of identical twins - obviously not of fraternal.

And, as Nava notes, DNA evidence that narrows it down to 1 of 2 people on earth can’t really be called useless.

I actually know a guy who slept with his identical twin brother’s wife. (Consensually- she knew which twin it was). She got pregnant, and the two brothers were in quite a conundrum, since there was no way of telling which of them was the father. It apparently caused some estrangement between the brothers for a while, though I think that ended when the husband slept with his brother’s girlfriend to get revenge.

Identical twin DNA is not 100% identical. IIRC it’s more like 99% and here’s a link

*Father of fraternal twins so an interested layman

We’ve threaded this more than once, I think.

Too tired now–it’s two minutes before whatever the hell time in the morning this is posted–or I’d do the search.