Rule of Three (Carnal Coed #3)
Suzanne Rock

Jag and Nolan share a deep, emotional commitment and wouldn't dream of letting anyone come between them--that is, until they meet Shana. The more time they spend with her, the more they bend their 'keep things physical' policy. As their kayaking trip comes to a close, the men must put aside their jealousy and reevaluate their rules on women, or risk losing Shana forever.
Note: This is book #3 in the Carnal Coeds Series and is a stand alone novella.
Other books in this series:
Two Are Better Than One
And One Makes Three