No. Although, you can't exactly tell until they reach "that age." Though there would be signs.
I would try to see if it is just a phase, and if counseling would help. However, if they were indeed gay, I'd be cool with it.
I personally don't think it is normal/natural, but it's not like you can prevent someone from being gay, so why should I disown them?
Then again, I'm not even sure whether or not I'd even have a child. I'm not even sure what the right age for me to even commit to something like that would be. I'd have to be wealthy/well off before I even consider fathering a child. It's such an enormous financial burden.
But having a gay son to decorate my house, and cut my hair would be cool, lol.