My daughter (swcah) was 9 lbs 3 oz at birth and at 1 year she did not even come close to doubling her weight. She is 2 years old now and she is just shy of 19 lbs and is 27 inches. Her weight gain slowed down at about  6 mo, and she has been tiny ever since. She is a picky eater, but she eats. They say that kids will eat enough to keep them alive, I try not to compare her to other ’normal’ (I hate that word)children, I just make sure she stays on her curve. Good luck.