Catholic philosopher Peter Kreeft (who has done great work against abortion) has an interesting (and provocative) article:
While he rejects the belief there will be marriage in heaven (see: Defending Latter-day Saint theology about Eternal Marriage), he writes the following:
Everything on earth is analogous to something in Heaven. Heaven neither simply removes nor simply continues earthly things. If we apply this principle to sexual intercourse, we get the conclusion that intercourse on earth is a shadow or symbol of intercourse in Heaven. Could we speculate about what that could be?
It could certainly be spiritual intercourse—and, remember, that includes sexual intercourse because sex is spiritual. This spiritual intercourse would mean something more specific than universal charity. It would be special communion with the sexually complementary; something a man can have only with a woman and a woman only with a man. We are made complete by such union: "It is not good that the man should be alone." And God does not simply rip up His design for human fulfillment. The relationship need not be confined to one in Heaven. Monogamy is for earth. On earth, our bodies are private. In Heaven, we share each other's secrets without shame, and voluntarily. In the Communion of Saints, promiscuity of spirit is a virtue.
One should pursue the entire article (and don't worry, it is very "clean" in language and content).