stepbrother ......problems

[rcgj]

so my stepfather had a son.....he lived with his mom, who died 4 years ago...until now he lived with his family...my step dad had high blood pressure and lost some memory, thats when my stepborther said he wanted to spend time with my stepfather. I dont beleive that, my step father owns 4 homes which is the reason why i think he really came. he has been here for 11 months. he only cut the yard once. he never takes his father to the doctor, i do. he never spends any time with him also......My stepfather and my mother dont trust him. They never leave my sister alone with him...before he moved in I knew it was gonna be trouble. I told my mom not to do it but she said she had to since its his son. When he came my mother told him not to bring people into the house. we always keep things to ourself...7 months later he got a girlfriend and brings her and they eat our food, keep in mind, my mom has 2 job to feed us..she even has a toothbrush here :/ ...i can hear them having sex from 3 rooms away its disturbing.......my sister was happy to have him there, but now she wants him gone...i tell my mom to tell him not to bring his girlfriend but she just gtes mad at me...she just says she has too many problems....and to tell his dad.....i tell his dad and his which agrees with me and wants him out also, tell me to tell my mom....so it goes back and forward..i tell them both together so they can do something and my mom just gets mad like always.....every time i hear something outside i look out the window. yesterday i did it and the girl said you have someone peaking out the window with an attitude..and i told him if she dont me peaking out my window then tell her to leave....he got mad and we almost fought........what can i do? every person in the house dont want him there including his dad. my mom is the only one that feels sorry for him