I need advice on how to separate myself from my step family?

My mom married a new man. He, in himself, is just actually infuriating. Anything my sister and I say is an attack on his children. He is a drunk. We cannot say certain things around him cause then he freaks out. He’s a piece of work. His kids are the main problem though.

His oldest isn’t as bad as the younger two. The oldest is a boy. Him and I are pretty close cause we are closer in age and have more in common than him and his sisters. The main problem with him is he does not know how to keep his mouth shut when talking to their grandma (a woman who hates my mom, my sister, and me.) Like the other day their grandma came over. She asked where my mom is, first off it’s none of her business, but he tells her she’s working another job to get money. And she says, “Well if those girls would get up off their fat lazy asses and actually do something.” Talking about my sister and I. We are in college and we’re lucky enough to have a mom who can support us so we don’t have to work during college. Their grandma is very traditional, and just hasn’t liked us from the start.

The middle child. Again she has a big mouth to grandma. To anyone actually. If you put enough pressure on her, she’ll give in. Cause of her younger sister. For example there was a daddy daughter dance and she wanted to go, but her sister bullied her into telling their father she didn’t want to go because she wanted it to only be her and her father. I think this is about all.

The youngest. Oh my gosh when I say youngest child Syndrom I MEAN it. Like OMG. Believes the world revolves around her. Anything she says goes. Her dad caters to her every whim. She literally threatened to pew pew the school WHILE SHE WAS AT LUNCH IN THE SCHOOL. Got caught, obviously, and got sent to the pods for the rest of the school year. What do her father and her grandparents say, “it’s not your fault. They took it too seriously when it was a joke.” “What ever happened to freedom of speech?” And because they made excuses for her she STILL believes she didn’t do anything wrong. Shes 13 btw and did this when she was like 12. #2 - she was like 10-12 when she was talking to a boy on discord whom she didnt know. Her father had no clue. Grandma knew. Her siblings knew. And we only found out because this boy sent a text to her brother saying, “I need you to r*pe and kill (blank) for me.” Telling her brother to r*pe and kill HIS OWN SISTER. And when they went through her phone because of it? A random boy who claimed to be her age. She sent him multiple nudes. This kind of language was common in their relationship whenever they would get into a fight. She sent HER AND HER GRANDPARENTS address to him. A RANDOM STRANGER ON THE INTERNET WHEN SHE WAS 11-12! Her grandma didn’t care. Her father cared at least. She also had a postal dude obsession. That started at 11. Her brother called her jail bait and she got so offended but then the next sentence that came out of her mouth was, “I just want an older man to take care of me and love me and my postal dude obsession.” She has a full on shrine to postal, I’m not even joking, pictures of him everywhere in her room, a stuffed doll that speaks, a body pillow (that she’s going to have a fake wedding too), bracelets made that represent him, little yootuze figures, and I could go on and on. #3 - her grandma buys her anything she wants. Which okay. Maybe. But she’s bought her lingerie AT 12. Playboy bunny outfits. Books like Haunting Adeline and the Caught Up series. And grandmas excuse, “she’s not innocent she’s seen this stuff already. They make movies out of it. I didn’t know what they were about.” And then proceeded to tell her brother, “I didn’t think she’d get caught with it.” She consistently calls her youngest grandchild a whore and slut like on purpose and because the youngest likes being called that.

And the middle and youngest continue to say they want to be closer to my sister and I, but their actions prove so much otherwise. And their father doesn’t help either. They also just don’t understand the meaning of empathy. They say their life is horrible (like in a serious woe is me way) and complain and complain yet they both have friends whose lives are worse than theirs. They aren’t able to put themselves in ANYONE ELSES SHOES. Because their whole lives their dad and grandma have been catering to them and making it all about them. To a point it doesn’t matter what anyone else is going through, it only matters what they’re going through. They also say they don’t want drama and yet they give their grandma all the ammunition to CONTINUE THE DRAMA. The youngest literally recorded my mom and their dad’s conversation to start drama. They continue to do it over and over and yet expect my sister and I to get close to them. Why would I give you ammo (stuff about my life) if you’re going to turn around and give it to someone who doesn’t like me and will shoot me in the back with it?

And what I’ve written down isn’t even all of what’s happened.

I care about them and I don’t want to see them hurt, but at this point it is hurting my mental health more than I can handle. And I don’t know how to distance myself from someone who supposed to be my family, because I’ve, luckily, never had to do that before. I don’t know how to be here with my mom and at the same time not care about the other people in this house. Cause when I go back to college here in a few weeks I don’t want to come back. But my mom and sister are here so I want to come back at the same time. I don’t know what to do and I’m tired and done with this whole situation. And I just don’t know what to do.