Fraud may include immigration fraud where one party uses the other to obtain certain immigration status. It may include fraud as regards a party's desire to have children or to live together in the same household. Or it may include that party's lack of desire to have relations with the other party.
A party may still be married to another person and never received a divorce from that person.
Nonage
Impotence
Duress
Incapacity
Incest