My cat Venus just turned 9 months old and at her most recent vet appointment she only weight 6 and a half pounds! Her dad was a 18 pound ragdoll and her mom was a 13 pound ragdoll mainecoon mix. Does she seem small at her age??
I do not worry about the weight of my cats, preferring to go by how they feel under my hands, how they look, their activity level. Most of my cats lived into their late teens unless they were taken down by some terrible disease or a predator.