Is there a strategy for Sims Marriages?

Are the Sims partners predisposed for each other? For instance, a Geek is attracted to a Flirt? I have a Geek and a Flirt and they are really kissy and huggy while 'Being Romantic'. But my Sporty and Flirt aren't. They mostly talk and maybe get a hug in there. It's just strange. Do you have to find their right match or it doesn't matter with this game? I'm curious because if they are to fall in love, it would be nice if they were actually falling in love. Am I thinking too much? Thanks for any help you can give me.

I guess I AM thinking too much.