That was my first thought. The parents could have had an open marriage.
There are always the zebras, as well: the chimera has already been mentioned, and rape. The last is that her parents brought the wrong baby home from the hospital.
But regarding the “He isn’t her dad” part. He raised her. He’s her dad. I understand the woman is in a bit of shock right now, but after the dust settles, maybe she will realize this in the end.
That’s a good point - does she match her siblings close enough to have the same mother? Only more tests will tell.
(But do they really want to open that door? What if one of the other siblings is also not a match for dad?)
My other thought is, how much older are the older siblings? Would one of them remember family friends and family dynamic very well around the time SiL was born?
The OP said the other sibs strongly resemble both Mom and Dad and each other. The woman with the bio-dad issue resembles Mom some and Dad not at all. Resemblance isn’t DNA data, but it’s a strong clue there’s no more surprises in the family.
As the story unfolds, the thing that impresses me the least about the confused woman (and some armchair advisors here) is the amount of trying to use false pretenses to obtain genetic tests or verbal testimony from other people.
Hint: If you have to go around lying to your family and friends to get what you think you want, that’s a real strong clue you’re screwing up and should change what you think you want.
Well, exactly. To get any further, she’s going to need one or more siblings to help isolate mother’s DNA. The only one who could really answer her questions about her mother is probably her father. Even if he didn’t know for sure, he must have had suspicions. (Unless he really doesn’t have a clue…) So sooner or later she’s going to have to drop the whole thing or come clean to at least some of her family.
Well last night they came over and we watched Bad Santa and had a bottle of Clos du Bois Chardonnay, which my wife and s.i.l loved but bro and I didn’t care for. The movie was mediocre. When the girls went outside to have a cigarette Paul told me that she told her older brother and after getting over the shock he agreed to take some tests.
ETA:
All of this would be easier if she knew I knew. Once that happens I’ll be able to find out more real time. Also I wish my brother would join up here.
Well, yes, but with the same gender parent there is also the fact that you consciously and unconsciously imitate them. Agree with the rest of the post though.
I obviously don’t know the details of any of these personalities. But SIL getting her (half?)-brother involved truthfully means two things:
She decided to be honest rather than sneaky. That’s a point in her favor.
This cat almost certainly will get the rest of the way out of the bag no matter what anybody else wants. To whatever outcome(s) good and ill. That’s a point not in her favor.
Now SIL, SIL’s half?-bro, SIL’s hubby, SIL’s hubby’s bro (our OP), SIL’s hubby’s bro’s wife, and some elder pals of Mom are all read in. We’ve long passed critical mass for the secret leaking out the rest of the way.
Hang on to our hats; it’s going to be a wild ride.
And pk: if one more person enters the story it might be about time to invent names for these people. Alice, Bob, etc., so we can keep them all straight. Or get SIL to start posting so we can have the story first hand, not third. 
Are these tests really good enough to differentiate between Scandinavian and, say German, Dutch or Lithuanian DNA?
My name is Pete, my brothers name is Paul, my wifes name is Bambola (Dolly) and my sister-in-law is Patty. Her mother was also named Patricia and her brother that she told is Francis and her “dads” name is Tomasz (sp?) but everyone always called him Tom.
Can we call the unknown father “Sven”?
We hung out with my brother and his wife last night. At the beginning of the night she still didn’t know I know.
I guess she is now using a genealogist who is working pro-bono. No idea what he’s all doing in her quest.
So we were diving last night (that’s what we call going out to dive bars. We like to try at least 1 new dive bar a month, and then go back to the ones we like).
Out of the blue S.I.L. says she wants to go to an American Legion post and drink there. 
I haven’t been to one of those in like 40 years. The one in the town I grew up in was notorious for serving under agers. They would have dime tappers of ten ounce glasses of Blatz. When I was 16 I only weighed 155 pounds so for under a buck I could get totally fucked up. sigh. Memories.
But I digress.
So we’re sitting at the bar and she starts talking to the bartender and asked him if his name was so and so and he says yes. She then tells him that he’s a match as a 2nd cousin for her on Ancestry and she also found him on Facebook and she wants to talk to him. Totally freaked the guy out. Turns out while this guy did have the same name as her match, it wasn’t the right guy and this bartender never did the Ancestry thing. But now he knows he was basically stalked because he shares the same name with the guy who did. All the while she’s doing this I have to pretend I don’t know why and keep asking her what she is doing to which she wouldn’t answer.
Later on I sternly told my brother that if she is going to pull this shit he’s going to have to tell her that I know. So he agreed. For about an hour she was uber pissed at him. But then she warmed up as she kept drinking. After the 4th bar (I, by the way, was not drinking) Patty starts going on that she wants to stop at the house of someone who she never heard of but matched as a 2nd cousin and talk to them. Paul went off on her that she’s not going to some strangers house at 11 at night all drunk. “You want to get arrested? Me and Pete will do it for you!” (my brother is also a cop). It pissed her off that she wasn’t getting her way, but I was driving and it wasn’t going to happen.
She calmed down but I decided if she’s acting crazy as a shithouse rat then, what was going to happen if she kept drinking? So I decided we’d call it a night.
:smack: Wow. Just wow! More to come, I’m sure.:rolleyes:
Based on your description of events so far I don’t really think this search is going to have positive or benign consequences. I’m guessing her chances of finding a live baby daddy father are 50/50 at best given the ages involved and is she going to stalk ever possible DNA lead to finally say what if she succeeds?
“My mother and your father/uncle/husband had me as an out of wedlock baby due to an affair 50 years ago… so deal”?
This is a bizarre quest at this point in time that will do little but damage people’s memories and reputations.
I agree, but it’s not my idea.
As far as reputations are concerned, I guess the more old friends of her mother she’s spoken to the more she hears lines like “that doesn’t surprise me. Your dad is a prick”. Revealing to her that their marriage wasn’t as good as she thought it to be.
As a researcher myself I might add that if she is tracking down 2nd cousins, they share a common great grandfather. I mean, it’s a lead, but there are several generations in between and that’s a lot of people.
Dennis
How about “Seven”?
“It’s a beautiful name for a boy, or a girl. Especially a girl - or a boy.”
Obviously both the OP Pete and his bro Paul need to be very, very careful not to do anything that looks like (much less actually is) using their official capacity to assist the SIL in her confused quest.
I won’t be surprised if the SIL gets more intent on this quest to the point that she tries real hard to pressure her husband into poking into databases, running a few names at work, etc. And this creating a real ugly situation in the marriage when Paul quite rightly tells her he’s unwilling to go down that path.
For darn sure no good decisions happen late during a diving session. Except yours to kibosh her stalker raid. Good move.
If everyone is lucky, SIL will discover a new and safer obsession. But that’s not the way to bet.
Good luck Pete.
My dude, your SIL is coming unglued and it could develop into something unseemly.
This does not sound like something that is going to have a happy ending, on any level.
Stay out of it.
Yeah, that’s not going to happen. The only thing I’ve done is come on these boards and asked if there’s any way to do this. As I suspected it’s pretty much mission impossible. If she finds the guy it’ll be by pure luck.
I think that’s why she’s seeing a therapist. In reality I usually only see my brother and his wife about once a month, if that (they live 40+ miles away). So I think what I saw on Saturday was just a tip of the iceberg.
I am glad that she now knows I know, though.
As I said earlier, if that’s a surprise to her, her mother’s friends are talking out of their asses.