Purpose of Sex
Largely falls into 3 parts: procreation, expression of love and sexual pleasures. Certainly NML argues for procreation (using faith and reason) though modern Christians place more on expression of love than previously. Even Catholics do as well but procreation remains as the main purpose for them. You should consider how priests, monks ect fit into this idea. Don’t forget Aquinas’ lack of marriage and children and his claim that as long as the majority do it, it doesn’t matter if the minority don’t. Utilitarianism allows it for any reason as long as it is the greatest good for the greatest number. Kant can only really justify it as an act of duty between two consenting partners. Expression of love is difficult as that is an emotion which cannot motivate a person’s moral actions. Having a child and the sexual desire are both consequences which further makes Kant’s difficult to apply. You also have to be careful about not using a person as a means to an end. For virtue ethics any could be considered virtuous. Expressing love is definitely a virtue and sharing your body with someone for their pleasure is also virtuous.