Lapin is Remy's cousin and boyhood friend from the Thieves Guild. He is both a master thief and one of the Guild's electronics experts, second only to Theoren Marceaux, and is a joker, always trying to lighten the mood.
Lapin and Remy were apparently very close friends and spent a lot of time getting into trouble together in their youth. Lapin risked going against the Guild Council and his family to warn Remy about the dangers of returning to New Orleans, in an attempt to save Rogue from the Assassins, after he'd been banned and warned him that the Assassins already knew he was coming.
Lapin also voted in the Vote of No Confidence that Theoren and Gris-Gris called when Remy was leader of the Unified Guild. He voted for his cousin, chanting 'Remy, Remy, he's our man, if he can't do it no one can'.