You are not imagining them saying rude things. A lot of times though, parents do say rude things. My mom was awful, she would say horribly mean things and act like it was no big deal or that I was just weak. My dad sometimes says rude things but he's generally a good guy and he's mostly nice, the only times he says mean things are when we're arguing about something, but he's no where near as mean as my mom is.
My point is that sometimes parents say rude things because well, they're human and they're parents. I don't think there's a perfect parent out there, and we all say things we later regret or don't even mean.

They obviously do not know how much they have hurt you. I think the best solution is to explain to them, in detail, why you think they are abusive. Have actual "evidence" like "On Monday you said this and it really hurt my feelings."
When I was younger I resorted to keeping a journal specifically dating the horrible things my mom would say to me, because she would always say she never said that. She made me feel like I was going crazy sometimes, but that's what a lot of abusive people do, they lie and deny.
Perhaps talk to them one-on-one, not together, because they might gang up on you and just make you feel bad and not listen to you at all.
You could even ask your brother, why he doesn't seem to notice or be affected by their rude remarks. If he asks what remarks, be detailed. Like, "Yesterday they said this and you totally ignored it or didn't even notice they said that. It would upset me if they said that to me, so how are you able to just ignore them when they do that to you?"