Well did she get a divorce and if so, was the property not sorted out then ??? Regardless of whether he has paid maintenance or mortgage contributions it is still a jointly owned property and she would either have to buy him out or sell the property and give him his share, however if the children are under 18 this might affect things. If she defaulted on the mortgage they would come to him for the payments as he is still liable for them. Whether if she disputed it she would get more than 50% I am not sure, but I expect someone more qualified than I will reply at some point. She needs to get urgent legal advice.