At 6 months old my son weighed 20lbs 8oz lol. But he was also very tall. I think as long as your baby is proportionate or not a concern to the doctors it's fine
Yeah you can't really go off others. I know some people's baby's are like 19 lbs at 6 months. Granted my son has always been in like the 2% range and he's small but can be normal. :)