We are having the same issue with our DS! He's 3 and he is also adamant this baby is a girl. We've tried asking for his help to find names but he will only suggest girls names. We have showed him the list with boys names and explained we don't know what the baby will be but he just won't hear of it. "I have brothers, I want a sister it's a girl." Is what he says. I have 3 boys so really the odds are for another and that is what I expect it will be (I don't care either way) but DS3 says it's a girl and gets quite upset if we try to say it might not be. I hope he will be ok with it if it is a boy, I'm sure he will eventually, but not sure how to deal with it of he's not ok at the start