AITA for not telling my BF that my half-brother and I are not biologically related? UPDATED

"AITA for not telling my boyfriend my brother and I are not biologically related?"

My (26f) “half brother” “M” and I are not biologically related. I found this out at age 16, but nothing in our family’s dynamic changed and it’s not something we really speak about. My boyfriend “Dan” (together 1 year) found this out over Christmas (we visited my family) and has since been really weird about it.

He says that first and foremost he’s mad I never told him. I don’t see why it would matter, but he says it’s something you would normally share with a partner after being together as long as we have and he didn’t think we had secrets.

I don’t think this is a secret or even an omission, it’s not some dark family history that you get told once you take an oath, it’s an ancillary bit of info that is either relevant or not. No one treats M any differently now that we know (and my dad always knew and didn’t care), so why would I go around advertising it?

Dan says he looks at my relationship with M totally differently now. He says he feels a bit weird about how he’s observed us behaving now that he knows we’re not even related (we are NOT Folger’s siblings so idek what he’s talking about). He says there’s a part of him that’s wondering if I didn’t tell him so that it would make our “lack of boundaries” less of a red flag.

Dan is not a jealous or controlling person I’m the slightest, so this has me quite shocked. He seems really hurt and worried about it and I’m wondering if this is a big deal and I’m just desensitised because it’s my own situation?

My mother has warned me about being close with M being a red flag to guys so I’m now second guessing if it really does look from the outside like I was hiding it? The reaction is so out of character for Dan I’m really starting to feel like I messed up but at the same time, I also don’t get why it’s a big deal that we don’t share blood?

What do you think? This is what top commenters had to say about the situation:

SPdoc said:

NTA. I’m sorry to say but Dan IS showing controlling tendencies here.

panic_bread said:

Your boyfriend has severe insecurity issues that he's trying to blame you for. Get away from this man. He is not partner material. NTA

Gerti27 said:

YTA. Who in the world doesn’t mention to their significant other this kind of information? If my girlfriend came out and told me today that her brother isn’t really her brother, I would be beyond shocked. It would make me question everything else she’s ever told me.

Proof_Option1386 said:

NTA - as you've pointed out, this isn't a Folger's Commercial (or a VC Andrews Novel). Your BF found out when he found out. There's no reason he should have found out any sooner...

HeyCanYouNotThanks said:

Jesus nta, you were raised like that siblings. No you not telling him isnt a red flag for anything. You being close to him isnt a red flag. Your bf needs to get over whatever popped into his head.

Neither_Ask_2374 said:

NTA. This is a red flag for your boyfriend not for your brother.

But then, she shared these updates to her original post:

because I saw a few people asking about what my mother said. She’s a bit conservative so I think she’s overreacting but this whole thing just reminded me. She mentioned it at a time when M and I were living together, and she said men might be uncomfortable because we’re roommates, and M is protective of me.

We also have matching tattoos, which my mother says is weird (but she also just hates that I have a tattoo so I don’t take that too seriously) and that he gave me a Cartier love bracelet that I wear all the time.

Also he apparently has a habit of touching my neck that she finds weird (I say “apparently” because yes he does this sometimes to steer me in a crowded room or a signal if we’re in social situations the same way you would nudge someone under the table to get their attention, but I don’t consider it a “habit”)

Edit 2 - when Dan said “lack of boundaries” he just means I tell M a lot of things and ask for his advice a lot. He does the same with me. It’s not related to anything physical

For anyone asking how we were meant to be related - My dad presented M as the son from his short lived marriage to his ex (M is 9 years older than me), so we thought we were half siblings. Turns out his mother and my father had separated by the time he was conceived but my dad went along with M being his “son” because he wanted a child.

Do you think this changes anything? One commenter thought so. ranchojasper said:

At first I was really offended on your behalf because I'm adopted and though my brother and I are not biologically related, he is 100,000% my brother and nothing else and I am wildly offended at the idea that there could be something weird going on between us because we're not genetically related. That's incredibly stupid, and boy was I side eyeing your boyfriend about this

But holy sh!t your edits really changed my mind. No, it is absolutely not normal for your sibling to buy you a multi thousand dollar piece of romantic jewelry that literally exists specifically for romantic relationships.

That is super creepy. And he's always touching your neck? Super, super creepy. I would've been way creeped out by your relationship with your "brother" even if I thought you were biologically related. All of that is incredibly, super creepy.

Do you agree??