Y are my sisters acting like this?

Ever since my parents died my oldest sister whos 19 got custody of me im 11 and my sis shes 16 and ever since my parents died the 16 yr old named sammy has been rly rly mean and beatin me up and tellin me that no1 loves me and crap like that and the older 1 has been actin like my mom and actin like my mom and defendin me and the house is turning into a war zone how can i get it 2 stop my sisters are starting 2 get into fights all because of me its been like 2 months and things have just been gettin worse the 19 yr old keeps gettin moreAnd more defencive over me and the 16 yr old keeps gettin meaner shes so mean now she broke the 19 yr olds arm how can i get this al 2 stop