They live in the sea. Even they have their mates. Everywhere they go, they go in pairs. The male doesn't know how to feed itself, so it rides on the back of the female. After all, it's just an animal instinct.
Animals have to mate in order to spread their species, their influence.
But if we don't want to have a part in that, we just don't get involved. Your mate can demand repayment on your old karma debts only if you get involved. Just don't get involved, don't get attached. Try to keep your mind strong and don't waver. Develop your perfections so that they're greater and greater, and these other desires will just wither away.