Getting irritated RANT

My stepbrother has lived with us for three years, he was only supposed to be here for a few months and then move out, the reason why he moved in was because him and his wife were divorcing after she literally tried to stab him in front of their at the time infant child. Well like I said he's been here three years, he's 33 years old and lives with me (17 almost 18) my mom and his dad (my step dad). So we have myself, my son, my nephew whom my mom and stepdad adopted as their own, my other nephew who is my step brothers son, and my stepbrother, my mom, and my stepdad. We have seven people living in a three bedroom home. My nephew had to give up his room for my stepbrother when he moved in and is now stuck sleeping in my moms room with them. Me and my son share a room, which isn't an issue. They have destroyed the room they're living in (nephews room) there's writing on the walls, all over his desk, my stepbrothers son drew all over my nephews height chart on the wall and it's completely destroyed and it had been there since he was two. My stepbrother and me share a bathroom, he leaves pee in the toilet, leaves the seat up, has left his pubic hair all on the toilet, leaves tooth paste all over the sink, does nothing to help with groceries, he leaves their lights and tv on when they go somewhere ALL DAY and doesn't pay any bills, he washes his clothes and the bathroom towels that he uses literally everyday. It's the point where he's wearing the washing machine out. My mom is as fed up as I am but won't say anything because my stepdad takes his side on everything and makes up some excuse for him. He says he's still here because he doesn't have money but has bought three vehicles since he's been here, two expensive tvs, an Xbox one, and all different kinds of stuff. If he would've been saving up he probably would've been moved out by now and he says he's going to be here at least another year. The reason we're all irritated is we all have had to give up MULTIPLE things while they have lived here, my stepdad won't kick him out or anything, he doesn't care because he looks at it as "well they're not destroying my stuff so whatever" because everything they've messed up has been my moms, paid for by my mother. When my sister (who is also 30) had to move back in temporarily with her kids, my stepdad made her life hell, and kept threatening to kick her out when she literally wasn't going anything wrong. I'm seriously about to go crazy here. Especially with the bathroom stuff because that's just disgusting and when my friends come over and have to pee I have to tell them to wait and go in there and inspect everything to make sure there isn't any pubes or pee anywhere.🤦🏻‍♀️