HELP? Opinions?

So I have a 3 month old son , and my babydaddy has another 3 year old daughter .. so she’s over at my house with my babydaddy ... and she keeps shoving stuff in my sons face , pinching him and all ! My baby is literally red all over his arms ! So I pop her on the hand and she goes and tells her dad and he gets mad at me and says “ they were only playing you had no reason to pop her “ and then he takes her to another room and tells her don’t touch or even look at her brother no more ? In a sarcastic way? Ugh I’m about to spazz .. he really shows favoritism ! And also ( not about this story ) but my baby is 3 months old and he posted posted not 1 picture of him? No post about him .. nothing but yet his daughter gets posted all the time ? Ugh idk ..