Six siblings are in the midst of selling deceased parents' home One wants to leave his share to girlfriend should he dies before sale Is this legal?

If your brother survived your parent and has inherited a share in the property he can make a will leaving his interest to his girlfriend. In fact, that's exactly what he should do if he wants her to have his share in the event of his death. Otherwise, his share would pass according to the state laws of intestacy to his heirs at law. Generally, his heirs at law would be his spouse and children or if he has none, his siblings.