Originally Posted by Pottsie
Revan = 24
Carth Onasi = 30
T3-M4 = 4
HK-47 = 6
Atton Rand = 23
Mira = 19
Bao-Dur = 23
Kreia = 75
Revan was already a knight when she joined the Mandalorian wars. The Mandalorian wars ended
5 years before the KotOR storyline, and it would have taken several years even for Revan to bring such a huge conflict to an end. Somehow I have trouble picturing Revan as a 15-17 year old Knight.
Carth is stated to be 38 years old in the game.
T3M4 was purpose-built by Janice Nall on Taris on order from Davik Kang, in order to aid in his plans to procure the passcodes allowing him to leave the planet. I doubt Davik would let T3 sit on a shelf for 4 years collecting dust before taking possession of his droid. T3 was an infant in KotOR, which may explain why it didn't have much of a personality.
HK-47 was, according to his own words, built by Revan at the beginning of her campaign against the Republic, which started ~4 years before KotOR.
Atton fought in the Mandalorian Wars for the Republic, a war that ended 10 years before TSL. Even if he joined just as the war was nearly over, being 23 in TSL would have made him 13 years old at the time. I doubt the Republic would conscript children as soldiers.
Mira was also in the Mandalorian Wars, on the Mandalorian side. If she's 19 in TSL, she would have been 9 by the time the war ended. Even though the Mandalorians probably are more "flexible" when it comes to using children as forced labor, I doubt a 7-9 year old would be of much use in carrying ammo crates and other heavy equipment.
Bao-Dur, same here, he was part of the Republic Military during the Mandalorian Wars, serving for some time under "the General". I doubt the Republic would use a 10-year old tech in their armed forces. (Though I admit it's possible that Zabrak have a shorter lifespan than humans and thus mature more quickly.)
As for Kreia, while it's possible that she is that old, the game (Disciple) suggests that she is actually much younger than she looks, and that her aged appearance is caused in part by Darkside disfigurations.