My curiosity's piqued...Assuming two people are married, what type of scenario is needed so that one can write their spouse out of the will so they get nothing? Is just having your name on bank accounts or any property enough? Also sounds like it could help OP if he knows his stepfather just can't give everything away to a nephew or the Army.
He can give away anything that's his, to anyone he chooses. Usually joint assets go to the surviving party regardless of what the Will stipulates.