We realized early on that there could be no place for jealousy in this kind of relationship. I've come home and discovered my wife and our partner together, I quietly will go about my business, but have learned to not be jealous. I have time with my wife and time with my partner alone, and the times together are the best.
Recently the two of them went camping together, it was kind of nice having the whole bed to myself. Last weekend our partner was out of town for the first time since the beginning of our adventure. It was nice being with only my wife for a bit, but we realized how much our partner had become a huge part of our relationship; we both missed her so much (thank God for Skype). I have to leave for a week soon and will miss them, then my wife will leave for a week for business.
This relationship continues to blossom and three of us couldn't be happier with how things just fell into place.