Maybe I'm the asshole.

So my boyfriend keeps pushing my buttons when it comes to my 5 year old son, me and him have a 7 month old daughter together. My son loves making her laugh so he plays peekaboo with her, he can be a little loud but she laughs historically to it. I cant even make her laugh like that ! Anyways, my boyfriend yelled at my son for yelling peekaboo too loud to our 7 month old. Anytime my son tries to have fun and bond with his sister its seems like my boyfriend has a hissy fit and yells at my son. I cannot stand it. There is more to this on how he is towards my son he seems very cold in alot of areas.