We have a V with my husband's best friend. It's been a wild ride! One thing we've been surprised by is how much closer the two guys have become -- sort of like, "blood-brothers," maybe? They are as close as two hetero men could ever be! It's been tough at times but we always bring it back to something good. Our goal is that no matter what happens, my husband and I will remain married, and we all will remain friends.
We are Butch Cassidy and the Sundance Kid.... and Etta Place
(See the movie, if you haven't yet. It's a great model, for our kind of V).