Perhaps you are skeptically thinking: is this topic serious? Or is it just a hoax? The answer is: it is serious. So before I try to answer the question, I want to justify the question.
There are seven reasons why this is a very good topic.
First of all sex and heaven are two things that we all are very interested in-- two things that we all desire, two great questions.
Secondly, it's good to connect great things. Very seldom are these two things connected. If you don't connect things, you get a chaos instead of a cosmos. You don't have a unified world view. You don't contemplate the beautiful, unify diversity. Is it only physically that the universe is connected by space, time and matter?
Thirdly, these are two great puzzles, two great mysteries. Neither one of them is clear. Heaven is too far away to see clearly and sex is too close to see clearly. And since we love mysteries [?these are two great puzzles]. Pascal says in Pensees that the human situation is always in the middle between two extremes or a number of extremes: too much light, too little light; too much distance, too little distance, [?] too. Gabriel Marcel says that the greatest questions in philosophy are mysteries rather than problems. That is, things that cannot in principle be completely solved or resolved because we're close to them: `union of body and soul', `why do we fall in love?'. How come no philosopher has ever adequately answered those questions? Because you can't get a sense of distance.
Fourthly, these are not just two great desires and two great mysteries that we have connected, they're two great realities. They're ontologically great, they're metaphysically great, they're objectively great. Not only do we feel profoundly about them, but what they are, what they mean is [?very] deep.
Fifthly this is a good question because there is resistance to this question-- a double resistance. First of all many people think that sex is too earthy a topic to connect to heaven. They feel ashamed about it-- it's not religious enough. Others feel the opposite-- that heaven is too religious a topic to connect with sex. They feel ashamed as if it's religious interference with sex. Some people I suppose don't want heaven if there's no sex in heaven and other people don't want sex if it's heaven [?].
In the sixth place, it's a good question because its a very concrete question. It's a child's question. It's an honest question. Most of the questions contemporary theologians ask are safe because they're vague and platitudinous. I wrote a whole book once: Everything You Ever Wanted to Know about Heaven but Never Dreamed of Asking because my daughter who was then about six asked me the question ``When my cat dies will she be in heaven?''