You would need to track down the genetic line of the fathers family, sticking to the male side only. If you can see a realy strong corrilation of one gender then it may impact on the likliehood of you having a particular gender, however as others would have said it als depends on the sperm and timing of intercourse and ovulation.

However My DH male blood line is very strong. His grand parents had 2 boys and a girl.
His uncle had 2 boys, he is the oldest of 2 boys and a girl, and we are now expecting our first, a boy, that;s either genetics or plain freaky. I would love to go back further through his history and see if the pattern continues.