What is his problem? I don't understand.?

You should really tell ur "mum" about this. Or you could move out and live with grandparents or soemthing if your just done with him. But you mom could try to tell him to stop. Maybe u could get ur sisters to tell him also and gang up on him. Either one will probably do the job. But if it gets from worse to worse then as I said before you have to move out. You can't take any more of his crud so just stand ip for urself! U can do it. :) best of luck to ya! Hope I helped!