My boyfriend got really defensive after I asked about a girl his family invited out: Thoughts?

So a little back story, my boyfriend is 16 years older than I and we have a child together. So his family member invites us out to do something with all the kids, we go, and we all have fun. Well, his family member brings a newly single female along. My boyfriend mentions something about her I ask when he and his family member ever talked about her; he says they never have. My boyfriend then says something about how she used to work at a restaurant we go to frequently. I ask how he would know as I’ve never seen her. Then I ask if his family member told him, he says yes. Well, okay, now we’re back to when did you and your family member talk about her? He gets defensive and begins yelling, saying I’m accusing him of something. Which I’m not; I’m just trying to figure out the whole story here as I feel it doesn’t quite add up. I told him the fact that he’s getting so defensive over a female he claims to not know is pretty suspect. He says I’m always accusing him of something or looking to fight. All of this after we both agreed to talk through things more so I would stop overthinking and so he would stop keeping things bottled up. How would you react in this situation? Do you feel I was somehow in the wrong?