If i Put Them out would i be Wrong?

Okay i went half on an apartment with my brother and his two girlfriends. the security deposit was $2000. So we moved in and we need some things for the house, like towels and cleaner. my brother and I went to walmart, so i'm getting the stuff that we need like mops and brooms and cleaner etc.... he gets a dog cage for his dog. we get to the line to pay and he puts his $100 dog cage up there with my stuff so that i can pay for it, he says he was going topay me back. he never did i asked hom for my money several times and never recieved it. one of his girlfriends decided that she wanted to move out(the one who was going to pay half the rent), she moved out so now it was me and my brother left to pay the rent. he goes to jail before we get to pay tha first motnhs rent. His other girlfriend gets aleats $200 a week but she doesnt feel like she should have to pay rent. the rent is $800 and i have to pay the entire $800 on the first. Would i be wrong if i tell her she needs to give me $400 or move out? i dont think i am i'm just tired of people taking advantage of me