Noah, Diane,
I'm not sure exactly how this works out either. To be honest I've been a little lost through the whole thing. Apparently when Dad and MIL divorced the house was something that they never settled on so it was left in both their names. It's possible that a will would get rid of the whole problem... unfortunately we don't think there is one but a will search is being done. So technically right now the house belongs to MIL and Dad's GF.