Minecraft entity changing

In short, i made a recource pack that make all piglins/Zombie piglins/Brutes fat. with Brutes being the biggest. What i need help with is that i dont want the fat model to transfer to the baby models too (Cause like, ew) so it there a way i can change the baby model seperate from the normal mob? Cause ive seen it done with baby animals in the game