Anybody heard of this?

My sister and her hubby adopted a pregnant (unbeknownst to them) female cat
a couple years ago. She had five kittens, they kept 2 and gave away three.
2 of those three went to one home and when the little-old-lady who adopted
them passed away my sister and her hubby took those two cats back in (now a
couple years old). One of them, is just enormous (not fat, just a big
kitty) compared to his siblings and the vet told my sister and her hubby
that this was due to his being fed kitten food for longer than the siblings.

All the cats are different sizes, one is downright lanky.

Just wondering if anybody else heard that feeding kitten food for too long
can cause a cat to grow larger.

Tx and Happy Turkey!
LeeAnne