IF this happened as told, and if I were in OP's shoes, my reaction would have been different. When psycho-woman came out with the bit about testing Lily's DNA against my brother's and there was no match, I'd have gone with 'I know, and as you're marrying my brother you're going to be a part of this family, so you need to know the family secret. My brother isn't really my brother. The baby my mum gave birth to was really, REALLY ugly so she switched him with a cuter one in the hospital. Don't tell anybody, though, 'cos the last two people who learned of it mysteriously vanished. Now, can I get you a coffee?"

(I promised I wouldn’t again tell my long winded history here in the comments, but it’s in previous ones) I’ve a similar stitch. Best friends hubby was KIA while she was in her 1st trimester, she was terminal & died shortly after childbirth. My husband & I went through the foster/adopt classes/process & have a beautiful 10yo son we took home from the hospital. We’re both men, so that’s a public challenge *daily* (given men with kids are often treated with suspicion) and we’ve completely different melanin levels than he. There’s no way he could have biologically been either of ours. You’d be amazed at how many people simply can’t mind their own business. You’d be frighteningly shocked with how many people, including law enforcement, believe that two men with a child is so suspect that it’s enough probable cause to suspend our constitutional and civil rights. We carry all his documents, because we’re questioned so often. We now are no longer detained since we carry the docs.

Oooh my! I would not be letting such a nasty person around my child unsupervised.

Why did the brother let this go on? He said his siblings knew he had adopted her, unless she did the test without his knowledge too. Brother and SIL are in the wrong.

We can't just roll past the fact that she obtained a child's DNA without parental permission, AND, when she got the results back she exposed all of this IN FRONT OF THE CHILD! Of course you're NTA! Your brother and his nosy, messy b**ch of a fiancée are firmly ensconced in a**holeville, and I would never speak to either of them again. Count me out of the wedding. I won't be at family gatherings if they are there. I'd make the same rule for brother that Michael made for Fredo: "When you see our mother, I want to know a day in advance so I won't be home." BTW, she is lucky that her little stunt in front of the child didn't get her a single-handed facial applause.

Don't stir the sh1t unless you're willing to lick the spoon ~ Wisdom of the Internet

Another phrase that I'd rather hadn't entered my vocabulary - "workplace shooting".

What should his response have been that would not have embarrassed her!? There is none. She did it to herself.

Why?! What could she have possibly gained by doing this?! Honestly, just why?!!

So sil and brother not talk at all? In the course of their 2 year relationship, the brother never mentioned the situation to her? Or when she did the DNA test, did she not tell him her plan and/or show him the results when she got them? Then he would've said "she's adopted"

You're NTA, actually you're one of the better humans around.

I would still be laughing in her face every time she walked into the same room as me.

The a*****e here is his brother who didn’t say anything to his wife about his brother and the adopted child.

Your brother better dych the bych before the drama really starts.

I think the brother couldn't believe it was a platonic relationship, gossiped with the SIL and thought it was a good idea to give his DNA to test. I think the brother planted that seed and she ran with it. Or, they were drunk and thought they would "catch 'em.

Run brother. RUN. Somebody who would do something like this will do some serious damage to you and any children you might have. NTA but even if you went nuclear on her out of daughters earshot of course, I think you'd be ok. some solid lines have to be drawn the first being that she doesn't EVER talk like that about either of Lily's parents like that to you or to Lily or behind your backs. No child needs to be hearing that. I can't believe she didn't know the circumstances if she's been with your brother for two years. If I were to take a guess she might be jealous of your daughter or rather her status and attention. Either way, Id minimize exposure. Because people who pull this s**t can damage families

Un-effing-believable! You laughed at her & embarassed her when she thought she was doing the right thing? Where do you get such ..... SELF- CONTROL??? My hat's off to you for your quick judgment of the situation & your measured response. That would not have been my immediate reaction - something indignant, smoke coming out of my ears, & my hair standing on end - but, keeping in mind that my precious child was in the room, trying not to explode like a volcano, & a very "unpleasant" conversation would have happened at an appropriate time & place, including your brother, since he saw nothing wrong in what she did. (Curious to know what OP's parents' reaction was.) But OP's laughing completely shot down whatever her plan was - burst her great big nasty balloon meant to reveal surprising, scandalous information, creating drama, painting herself as the heroine for finding out & telling OP & everybody else, the "truth" they all needed to know, for their own good.

OP is right. SiL embarrassed herself

This is evil wicked behavior,. I'm thinking she is a self righteous, gossip hungry bully at heart. The viler the gossip she can be a part of the better, and probably no problem dispensing what she knows to be out right slander. She wants to be the biggest part of any information exchange but rarely, if ever, is.She knows the true story after 2 years with your brother, but considered it a cover-up and was polishing her halo by exposing the truth??huhn ?? It sounds like you've missed a salient point, she wasn't telling you, she was purposely telling your daughter, hoping to hurt her, I'd say she firmly believes in the sins of the parent ( with her as upright purveyor of truth). You embarrassed her by being on the hearing end of her vitriolic behavior and countering it with said already spoken well known truth?? If your brother is defending her in this he may already be lost to you, cuz I'm sure after 2 years he's got to be fairly well acquainted with this poisonous predilection.

Your one in a million by adopting this sweet child. That makes you a decent human being ..no matter circumstances. The SIL and brother ...well not so much . Your brother allowed his girl to use his DNA and steal a child's DNA . He's not the brightest tool in the shed. By her confronting you in front of child was the lowest, sickest , depraved, jealous thing a low based human can do. Sounds like she wants drama and you. Was she hoping you would give up child and be open to an affair behind brothers back? Seems her intention. If not she's still a drama seeking pos. Do not allow her around your daughter and tell brother he better be watching his girlfriend for chrating...cause she has to have a drama filled life and she's bored.

Busy body, needs to mind her own business and maybe now she's learned a good lesson

The brother isn't that kind either by the looks of it. It even states "My parents and siblings know that my daughter is not my biological daughter". So the brother knew the situation and instead of saying anything, let his fiance look like an idiot. So let's be real. The brother and fiance are probably perfect for each other

Holy Cow! This is some no contact territory. She dropped her mask. He cannot have that woman around his child.

The only person there when she was embarrassed, was the daughter, who she was trying to embarrass

Yikes.

The brother was as bad as his girlfriend for going along with it by giving her his DNA. I would steer clear of them in the future. She’s probably the type who will make constant jibes towards your daughter. Evil bstrd is what she is and your brother isn’t much better

Brother is a wussy to think she did no wrong. Cut ties from both.

Since she was studying the portrait of you, Lily's parents and then somehow decided she needed to test the child and HER HUSBAND, I think she saw some form of family resemblance to him, not to you. Probably hoped her hunch about her husband not being the father would trigger you being the father. Sometimes drama queens get too deep into their own lies. She was most likely looking for answers she hoped wasn't true and then decided to go the way of hey, your daughter isn't yours! (Thank goodness my husband isn't her father either!) Type of stuff. But sounds like this woman has some very deep seated issues overall! I'd for sure not allow my daughter around her anymore.

The SIL is the kind of woman who would commit escalating levels of abuse against any child of her husband born with another woman for having the "audacity" to exist!

I think you posted this for click bait and haven't read the follow-up post.

I've had experience with this type of person. They think it's their right to broadcast people's private business/problems, and then expect a pat on the back for "fixing" said private business for them, but never take responsibility for ruining people's lives or marriages. Did she want you to abandon a little girl? Did she want her to remember the label "affair baby? Did she want to diminish your little girl's place in your family? I would tell my brother that she will never be allowed in my daughter's presence again.

9/10 when she has kids they won't be by the brother in law. She is cheating and deflecting. Sees it everywhere she goes because she is doing it or will do it. Brother needs to run.