BOYFRIENDS FAMILY RANT

My boyfriends birthday is tomorrow and his whole life he's been treated differently than his 3 sisters (2 older, 1 younger). He is always the one to blame if something goes wrong (even if he had nothing to do with it) and his Dad isolates him to do the housework and give him money. For the sisters birthday in a week, the Dad is planning a big boat party and getting her all kinds of stuff she wants. My boyfriends birthday is tomorrow and his Dad forgot and is now being angry towards him and saying he's not gunna get him anything or even be home. My family is throwing him a party and buying him some gifts, but he's depressed about the whole situation because my family has always supported him more. Last Christmas his dad got him nothing and my family came over with gifts for him and cards. Holidays we go with my family because he and I aren't  invited to family dinners. He hasn't done anything, his Dad just singles him out for no reason. I want to cheer him up but I don't know how, ideas????