I have a big baby, too! She was 10 lbs 7 oz at birth, and was 20.4 lbs at her four month checkup. And 28 inches.
She is just over six months now, and she can wear 18-24mo clothing with the legs and arms rolled twice.
My husband is 6'4" and everyone in his family is over six feet. Her cousin was also a big guy, but is now only in the 80 percentile now that he's past a year.