I do worry about my girls, at the moment though they are perfectly fine and well within the 'range' for their ages.
BUT
Growing up i was the girl with the bigger more 'athletic' build, the problem with that is i NEED to be super active to stay within my limits, i'm a big girl, i'm overweight and throughout the years i have never been SKINNY, i was always a little bigger no matter how fit, no matter how well i ate.
My girls are super active and i intend to keep it that way, teach them that eating well and being active is the key to be HEALTHY (notice i don't say SKINNY).
DP is quite big, he has always been big (nickname was chubbs) - majority of his family are big - think short people, big build.
My family are Tall people, big build - my mum is obese, my dad has a decent beer gut (rivaled my PG belly) but he has always been active and eaten well.

I hate that people look at a chubby child and automatically assume they eat cr@p, they dón't exercise etc etc.
There is a little boy in DD2's swimming, he's about 4mths younger than her and weighs as much as DD1 - he has so many gorgeous rolls and already wears size 4 bathers BUT talking with his mum this kid eats almost exactly what my girls eat, he exercises and is just as active it's just that he is a bigger boy and he is GORGEOUS.

I'm trying to keep myself thinking positively, the things i know now as an adult can help me with my girls... i don't and won't restrict nasty foods, i encourage them to get outside, be active and enjoy gettings muddy & messy and i will teach them that moderation is the key... i'm working on all of this myself at the moment and it's these things i didn't do as a teen/adult that would have made a HUGE difference.