Hey, don't make me feel bad. We managed to get 10 pounds on him in the last three or four months. : )
(My kids are all very small. My 2 year old is only 22 pounds, but perfectly healthy.)
My 18 month daughter is 28lbs, she's also the size of most 2 year olds. She's been in the 96%+ all her short life. Now her old man, me, I'm a big guy: 5'10", 205lbs, waist 33-34 (depending how much beer I've drunk for the day). I work out 3 times a week and yard work 1 more and according to the government I'm obese. :0) But I was a scrawny little guy till around age 25.
I'm short too (5'9", 159 lbs) I was always one of the smallest in school, and got teased for it a lot.