Boys! If I've told you once I've told you a thousand times: That's NOT what stairs are for! Go use a bed like civilized people. If I catch you there one more time, you'll BOTH be grounded. I don't CARE who started it!
As with any endeavor in the lifestyle, a ménage à trois success relies on laying all the cards on the table. Take time to talk about any fears, hang-ups or insecurities each of you may feel before searching for a third party.