In California there is a statute (Civil Code section 1624) known as California's statute of frauds. This statute requires that any agreement to pay for an obligation of a third person must be signed in writing by the person who is sought to be bound by it.In your situation if you solely made an oral agreement to pay the obligation of a third person and nothing more, then under Civil Code section 1624 you should not be bound by this oral promise unless you signed some written document (as well as dated it) stating that you would be bound by it.Given the fact that your former girlfriend's or wife's father is deceased, it makes her burden even the more difficult to prove against you concerning the oral promise.Good luck.