So, when first Tom O' Seven appears with Lord Beric's outlaws, he eventually says that he had some troubles in... Riverun or the Frey's palace? I don't recal...
Anyway, after Lord Beric's (look out, here goes a spolier of the fourth book) passes his life strenght to Cat, Tom remains with the Freys. So he wasn't there when the Red Wedding occured.
So when Edmure (ops... here goes another spoiler) meets Tom at the siege of Riverun, and Jaime orders Tom to play for Edmure, the latter says exactly:: "No. Not him. Get him away from me." So... has this two met before? On what circumstances?