Whoever ventures into this territory, should not underestimate the power of oxytocin (the bonding hormone), which usually comes into play quicker for the female than it does the male. And, if you have never done this before, no matter how much research you do, you will not know ahead of time how each of you will really feel before, during and after the event, either personally or about one another, as well as how you will feel about the 3rd party. Perhaps most importantly, you should also know before going ahead with this that it could break up your relationship, so it may be a risk you may not be willing to take.