Immuture mom

So for years my mom has been dating my dads brother ... her and my dad used to be married and they had 3 kids together but when I was about 15 his brother got out of jail and started dating my mom at first it was a secret but then on Christmas they came clean me and my siblings were mad as time went on my UNCLE started hitting my mom and telling my mom not to buy us things we didn’t deserve it we were good kids not fast running the streets when we would go to a friends house around the corner he would call our phones and lie saying things like your mom said get home now he would make us delete our social media account check our report cards and even tell our mom to kick us out and she would do it 10 years later my

Mom lies and says she doesn’t remember and that all that never happened my sisters love him and I just don’t feel no way about him today they are always telling me to give him a chance but my thing is everytime my mom breaks up with I’m she is always around her kids but when they get back together she treats us like peasants and doesn’t talk to us and when I confronted her about it on nye she got mad and said I was jealous and then me and my younger sister got into it because she is always siding with my mom , my mom acts like a child and the things she post on facebook is like a teenager going through a phase she even lied telling Facebook she had sex with a girl she said she’s done with my son I don’t know what else to do I’m open to all opinions please no rudeness