Large babies run in my family, too. I was slightly large at 8lbs, 4 1/2 oz and 22 inches long. My younger brother was almost 9 lbs, but he was 24 inches long!!!!! Two feet! Can you imagine? I suppose we have long babies rather than heavy ones. I'm now 5'8 and my brother is 6'4. This is my first, and he has measured large for dates at all my ultrasounds.
Believe it or not, my a close friend of our family and his wife had 2 boys, the oldest was 12 lbs and the youngest was 10 1/2. They were both vaginal births with no GD. So I guess it can happen! This friend also weighed over 10 lbs when he was born, and had an older brother who weighed 13 lbs. They were born to a tiny german lady who never weighed over 120 lbs and smoked at least a pack a day (in the 60's when noone knew better.) I'm just hoping my baby is a manageable size!