Family real estate problem need help?

-my grandpa died and was married at the time of his death but the woman he was married to they have been split up for over 10 yrs why he didnt get a divorce idk. My brother lived with my grandpa for the last 8 years before he died. He left power of attorney to my aunt well all the family agreed to give the house to my brother if he paid what was left on the mortgage which was like 4 years so he has been payin for the past year. What im tryin to ask is if hes payin the mortgage will he get the house but my grandpa was still legally married but they were split up for over 10 yrs or will she have the say so but she cant afford to pay the mortgage so if my brother dont pay it the house will be taken by the bank so any help please