You are right. In dreams sex generally has to do with wanting intimacy, not actual sexual desires. It can be really disturbing when you wake up and realised that you have had a sexy dream about a relative, but its common and understand that it is just a metaphor for wanting to be close to that person.
Apparently the symbol for sex in a dream can be anything from walking through a doorway to stabbing someone! Dreams are a little cryptic and really the best person to interpret them is you, just go by how you feel about them.
Hopefully you will not go there. I have two beautiful daughters. One 21. The other 17. Don't think that the thought never crossed my mind. However, it is not within bounds. Think of the ****** up relationship you would have there after? Please dismiss this thought. The act will hurt you.
lol @ zhafar!!
Just chalk it up to a dream and nothing more.
it is normal to have dreams.
Up to you to control yourself