I have a serious question it is fairly long ..?

ok my nephew who is 10 and been on meds for his whole life is acting out majorly(throwing things at people, beating people up , threatening to kill his own mother he now has disorderly charge on him ) now im not saying this is right but he has been basically yelled at for 10 years straight hes never really been sat down and listened to or talked to ..anywho the other day my hubby and i sat down and actually talked to him without yelling involved we also listened to him without interupting he told us that he wants to cry sometimes but he cant (think it is the meds my sis had that prob too) he does not have his own room his sister has to go through his rooom to get to hers his dad is in jail and his uncle can not come to visit him right now (THOSE WERE JUST A FEW ISSUES)and ive tried talking over the phone with her today bout the issues(lower the tone in the house give him his room etc but she was not really listening to me i dont think anywho she said the other day that he is an a...hole and she will not listen to a word that comes out of his mouth so im thinking im gonna have to go over there sit her down eye to eye and have it out with her ...my question is how do i get through to her that he is a 10 year old boy and he needs to be taken off the meds they obviously aint helping and i dont think he needed them in the first place(she is a very loud person )since hes been born ive only seen her show love to him 2 times im going out of my mind cause if this continues he will end up hurting someone severly i do believe that he just needs someone to talk and LISTEN to him but as i said my sister is a very stubborn loud person! i know yall dont know me but please help (he has had the police called on him quite a few times so yes he knows them and they know him )