Cub Simba and Nala sound like about 10 years olds but looked like less than a year old in lion years. But I don't think they'd age that quickly each year if a lion's old age starts from the tenth year and they may live for 15-20 years.
Soo...
I've always imagined:
- Adult Simba is about 5-years old in lion years and about 30 years old in human years when he claims the throne.
- Same goes with Nala of course.
- Mufasa at Simba's birth I've imagined about 8 years old in lion years and about 50+ in human years.
- Scar I think was from the same litter and thus the same age.
- Sarabi I'd like to imagine a bit younger than Mufasa, perhaps 6 lion years / 40 human years at Simba's birth.
- Timon & Pumbaa seem like young adults at rescuing Simba, perhaps about 30 human years and then couple of decades older just like Simba, when Simba's an adult.
- Zazu at Simba's birth doesn't say a word so it's hard to say. At Simba being 10 years old, Zazu seems like 30 years old in human years perhaps.
- Rafiki... Well, he actually looks old. His voice however is a bit unclear for the matter. 60 human years at Simba's birth? Of course that would make him really ridiculously old at Kiara's birth but so would be many others.
)