Relationship problem

Can someone please give me advice? So my mom and dad are super rude to my bf for no reason and are disrespectful to me too. They say things like “ omg he won’t want to marry you because you let him have sex with you” keep in mind I’m 19 years old and my sisters lives with her bf under the same house. Idk what to do because I understand he’s upset but it feels like he takes it out on me with and attitude? I tell him things to rant but it seems it’s always about him. His family makes mistakes too and does thing even he doesn’t agree with? What do you guys think I should do ? I feel like there’s only so much I can take before I snap and say something hurtful.