The Xandus were a marriage-less society.
They didn't need to bind themselves with each other.
If they liked someone, they approached them and expressed that liking. If the other party accepted, then they formed a contractual relationship that lasted from anywhere between 6 months to two years. There wasn't any obligation other than sex. Either party could demand nonstop sex for hours and days if they so desired. The Xandus lived 269 years on average. So, in a sense, having an eternal contract would only hinder their well-being and they'd figured it out sooner than later.
But having so much fun came at a consequence, namely children. Both Xandu men and women could get pregnant. Even two women could get pregnant even if no man was involved. In a sense, their society really didn't need 'gender' anymore but since men still had dicks, they just rolled with it.
