A lack of faithfulness in romantic relationships is often called a lack of morality. But things become less clear when taking a closer look using Hohfeldian incidents: while it is only supererogatory not to have sex with someone else than one's partner, not prohibiting them from doing so is a moral obligation to protect their liberty to act freely. There is no significant difference between having sex and other activities like playing football or between genuine friendships and good romantic relationships. Thus, the latter should, like the former, focus on the joy and positive feelings both parties can get - with each other or a third one.