How would you feel?

So I have a 2 y/o son from my past relationship, and me & my boyfriend have a daughter that was just born on sept 3…

My boyfriend’s mom invited us over today and it wasn’t until my daughter was born that she started making joking remarks towards my son. He’s very shy so he clings to me and he stands in the corner when we walk into her house and she says “If you’re gonna be a part of this family you can’t be shy. This family is not shy.” So I wipe it off and I get him comfortable to come into the living room. I ask him if he’s hungry and he tells me “no”. As I thought he would because again, he is shy just like me. He warms up to play with the other kids and my boyfriends mom says “(my son) will eat at some point today.” Wipe that off too. But now I’m sitting here thinking, why is there small rude jokes being made towards my son? Is it because he isn’t blood family and my daughter is? I don’t get it. My son is so full of life and love and wouldn’t even hurt a fly. Why is his shyness being joked about? Am I overreacting?