My DS was around 11 kgs when he was 12 months old... but he was 10 kgs at 8/9 months so didn't put much on. He's now only 11.5-12 kgs at 17 months old. He was a big baby right up to about 6 months old when he got sick over & over and lost a lot of weight...now he's one of the lighter ones in our group of kids the same age.