Oh, and I forgot to add, would "Fluffy"(young Kopa in my version) be at infant or newborn stage?

Well, Kopa had a hairtuft but DIDN'T have arm hair. Maybe hair is just varying in growth rate and styles and arm hair in cubs is a outlander-type lion trait. Because, we already know Kopa's hair would be like Kovu's as an adult because of his hairstyle. xD, just a thought. BTW, I almost died of cuteness attack with those baby cubs .

Guys, thanks for pointing those things up. I understand that animals age and die much more faster than humans, but I decided to don't use that logic, like Malta said, I was making this ages basing on human ages. Since Lion King is a cartoon animated movie where animals have some human features, I decided that maybe they're aging process could also be somehow familiar to the human's.

I think a cub that is 1 year old in 365 days. Eris could explain it better

Like what would a human look as a 1 year old? Or a cub that is 1 year old in 365 days old?

Cloudstar: I think Eris is just showing humans age

The render and the description is very useful,but the ages are a bit messed up :/ A 1 year old cub would already be up to his mother`s chin,and 3 year old would already have his mane heavilly growing,and fully grown.Just take a look at this useful site: http://livingwithlions.org/mara/how-to/age-lions/
Believe me,everything is useful and good,just the numbers are off.Keep it up

It would be useful!

This is interesting I like how you explain what the cub looks like at different ages

Hmmm...interesting, this could be helpful in the future ^^