On 2.08 Shyu says, that his father, among other sages, was forced to serve the Fire Lord when the war began. But i didn't find this info on Kaja's page, Why tho?
It also brings upon a question about Kaja's lifespan. He seems pretty old by the time he trained Roku (let's say he was 40-60 y.o), and given Roku was 27 back then, by the beginning of the war Kaja was supposed to be like 95-115 y.o. Does it make sense? I mean it's possible, but still. And also his grandchild Shyu was born 40 years after the war began, which means both Kaja and his son fathered their children by a pretty old age. Which is also possible (hey, Sozin and Rina), but i was just confused about not seeing all this stuff on wiki, so just checking if i got everything right.