Thinking of an odd comedy...

[Joe the Destroyer]

I saw a comedy late on HBO one night (ahh... so many b-movies I've seen on late night HBO...) and the premise was something like this:

A dying rich man says that he will leave his money and estate to his children (son and daughter) if they can just have kids of their own.  The problem is his son is gay and his daughter is a lesbian.  So, they try to actually be heterosexual to gain the inheritance.  I do remember one scene in particular where the son is about to get it on with his sister's girlfriend.  To try to make things easy, he dresses up as a woman and she dresses up as a man. 

[Yaddo 42]

It sounds like Too Much Sun

http://www.imdb.com/title/tt0103100/

Check it out and see.

[Joe the Destroyer]

That sounds about right, but I'd have to see the movie.  Thanks for the post!