This story fills me with a sort of unholy glee. Destroy an old man's belief in his 21-year marriage to your mother? Give him is freakin' $40,000 back.
http://www.nlrg.com/family-law-legal-research/bid/85594/FAMILY-LAW-Common-Law-Marriage-Mistaken-Belief-in-Validity-of-Marriage
http://www.nlrg.com/family-law-legal-research/bid/85594/FAMILY-LAW-Common-Law-Marriage-Mistaken-Belief-in-Validity-of-Marriage