My SIL is pregnant as well (funny convo with my brother when I called to tell him my news, since they'd just found out their own that day) with their 3rd kid. I taunted them with the first two, because they wanted a boy, and I told them it'd be a girl, both times. I noticed a genetic pattern with my dad's family...
Grandpa's generation: 1 girl, 2 boys
Dad's generation: 2 girls, 1 boy
Our generation: 1 girl, 2 boys
In that exact order. So, of course, I told him that he'd need to have 3 kids to get the boy. Now I get to see if I'm right.
(8 weeks!)
Of course, this sort of pattern makes me worry that I'm having a boy, since there's a sad lack of girls in his father's line.