[quote="Thegeni99"]that's true, he mentioned he was never incorporated in Disney stuff, he just felt like making the books, I wonder how they were even published
[/quote]
I believe Disney gave the book writers permission to publish
The Lion King: Six New Adventures.
Now, back to the topic. I researched that the average life span of an African lion in the wild is 10-14 years in the wild, while the average life of an American is up to 75-80. However, I couldn't find any reliable source that would convert lion years to human years, so I would estimate 1 lion year equals 7 human years. It's also best to use the filmmakers's words to theorize the human ages for the characters, if any.
Young/Adult Simba: An
August 1993 script written by the writers states Simba a full-grown cub, so he would be relatively a 6-month cub so, he would relatively be a 6 year old if cub Simba were a human child. As an adult, Simba would be about 35 years, as I predict Simba is a 5-year-old adult lion (due to that male lions are capable to challenging another male by that age) towards the end of the first film. So,
Simba's Pride, Simba is in his 40s during the first half, and early 50s during the second half.
Young/Adult Nala: I believe the same theory about Simba can be applied to Nala, though the filmmakers have never confirmed that Nala is older or younger than Simba.
Mufasa: Mufasa is certainly older than a 5-year-old in lion years, as he's far capable of challenging another lion or any other animal, so he's most likely in his 40s by the time he died.
Scar: Although Scar is the younger brother of Mufasa, the film never specifies how much younger than he is. So, I speculate that Mufasa and Scar are born in the same litter, though Mufasa was the first-born, which means Scar is also in his 40s by the start of the movie, and in his 70s when he dies.
Sarabi: Possibly the same age as Scar or Mufasa.
Sarafina: No clue.
Young/Adult Kiara: In the film, Nala tells Simba that Kiara is "just like you when you were young" so cub Kiara would be 6 human years. Based on Rooney's words below referring to Kovu's age, Kiara is a teenager as well, but relatively a year younger than Kovu.
Young/Adult Kovu: Cub Kovu is slightly older than cub Kiara, so he would be about 7 years. On the
Proud of Simba's Pride documentary, I recall director Darrell Rooney mentioning Kovu is a "teenage killer". Therefore, adult Kovu is actually a teenager.
Nuka: Nuka's age really confused me, since I didn't have the filmmakers's words to fall back on. So, I speculate Nuka, during the first half of the movie, is a 2-year-old based on his underdeveloped mane so he's probably an adolescent, therefore 14 human years. By the time, Kovu is a "teenage killer", he is in his 20s.
Vitani: Although unconfirmed by the filmmakers, I speculate Vitani and Kovu are littermates since they appear to be congruent in size and shape. Therefore, in my opinion, Vitani is also a teenager, but older than Kiara.
Zira: This one confused me more than Nuka did, but I doubt Zira is in the same generation as Scar and Mufasa, because she would be too old to bear her own cubs, so I speculate Zira is slightly older than Simba. Maybe, Zira is her mid 50s in human years throughout the second half of
Simba's Pride.
Timon, Pumbaa, Zazu, Rafiki, and the hyenas don't seem to have age at all throughout the films.