I *think* boy, based on family tradition (like that means anything. LOL!) and the skull theory, but it is a close call. Baby #3 does have a high forehead and a pointier chin, but the forehead *is* rounded and not so flat. The first two, on the other hand, are textbook cases of male and female skull characteristics.
Here's what I mean:
Below are pictures of my 1st (boy), 2nd (girl) and third (unknown) pregnancies, in that order. All the ultrasound pictures are at 12 weeks. Of course, they are all quite different, but the girl (#2) SCREAMS girl. High, flat forehead, pointed chin. I didn't know about the skull theory then, but if I had, I would have not been so surprised when I found out it was a girl.
Likewise the boy is almost textbook male, with a rounded forehead and rounded chin.
(By the way, hello fellow Ontarian!)