Tiny babies
On the 2nd dd had her 9 month we'll check, she's 16lbs 12ozs. So in 3 months she only gained a little over a pound. Which is normal since she's becoming more active.
My middle daughter was like that too. She was in newborn for like three months and wore size 3 for a solid year. Her and her brotger weigh the same and they are 21 months apart. She gets use out of her clothes and shoes when my other two dont. Im learning to appreciate it ahaha.
My daughter is the same way. She will be 2 in a few months, and still only weighs 18 pounds.