AITAH for ruining my own birthday

Okay so to start the night was fun up until; the last hour but unfortunately it was off putting enough that it ruined the evening for me.

lemme set the stage. I (30 female) went out for my birthday with my sister (34 ) and mom (58) and it was all fun until this happened. We were drinking, playing pool, very obvious that we are a group since we are giggling and walking around the table and have been for awhile. we have empty drinks on a table with our stuff around. even at the glance you can tell we've been drinking and are together in a group. It was my sisters turn and after she took her shot a guy walks up to her, which isnt uncommon she's very pretty, happens at least once every time we go out and its usually fine. But he puts his back towards us, separating us essentially.

Immediately I clock this guy as a creep, its 30 minutes to last call and he just isolated my sister from us to get her number. Zero acknowledgement to the rest of us not even a hello, we were invisible. which dont get me wrong, my sister is pretty, but wow. it was only when my sister said "no im married im out for my sisters birthday" and pointed to us did he introduce himself in the classic "no way youre her mom? not possible". cliche

I should also say that we weren't far away from her when he did this.. We were in mid conversation, maybe 3-4 feet apart and he placed himself in-between us making it so we couldn't talk to each other until he moved aside.

So right off the bat I'm stand offish. He tries to shake my hand, I keep my arms crossed. "Hi im chad (I assume)" me, "hi im the sister, the aggressive one, and who the fuck are you?" (Ive had a few drinks at this point. probably would have worded myself different but still would have been stand offish) he laughed and says "haha im chad whatever his name is" and I say, "ya that means nothing, how do you know my sister and why are you here?" at this point both my mom and my sister and mouthing to me 'be nice', I dont have the will power. "haha come on I drove an hour and a half to get into town. I just thought she was gorgeous dont be a dick". which to me just said "come on dude dont cock block me". After that I was just mad, my mom saw, she grabbed my hand and started talking to him instead. flirting with him even, they both were. huge ass smiles on each of their faces while Im very clearly uncomfortable. At that point so I grabbed my coat and went outside to cool off because I couldnt believe they were both entertaining this guy when they're both married with families, and talking about issues they have with their spouses but thats an entirely other thing.

my mom tried to come out to talk to me, I wouldnt have it. After awhile I went back in, spoke to my sister, she was defensive, saying she didnt feel threatened and she can handle herself. Which...whats fine but thats not why I was upset.

Im not normally a bitchy person, Im very polite unless I get a weird vibe or you do something off putting. I used to be a horrid people pleaser so unfortunately now I make up for it by protecting my peace like a pit

I feel hurt. Feeling like my family didnt have my back when clearly I was uncomfortable. Had he introduced himself to us normaly instead of singling her out, I wouldnt not have gotten a gross feeling, but he singled her out when it was clear she was with people chatting and that made me wary. AITAH for essentially ruining the night by only taking that experience home, or was my defensiveness justified?

EDIT: yes. IM VERY AWARE I can be extra. But I stand firm with the he gave me a bad vibe thing.