There's about 100 different stories of "player X was caught with player Y's wife), but as far as I know, Leeman/Iafrate is the only one where there's actual proof.
Although apparently Shanny is married to an ex-teammate's ex-wife, but I don't know what the actual timeline is (I'm assuming there's no scandal).
- Atomic Wedgie
Lindros and Brind'amour's wife.
Brind'amour was traded to Raleigh about a month after it happened and the divorce papers went through a year or two later.