Okay in the first season of Legend of Korra we learn that Tenzin is 51 years old and Lin is 50 years old. Now we know that Bumi, Kya, Tenzin, Lin, and Zuko's Daughter are the only known children of Team Avatar. In Legend of Korra Book Spirits Tenzin said that Bumi is the oldest of them so that pretty much confirmed that Bumi is the oldest child of Aang and Katara. But now I'm curious since Bumi is the oldest sibling he got to be aleast in his late 50's or early 60's? So I'm thinking that Bumi maybe the oldest child of Team Avatar or we pretty much have to wait more information about Zuko's daughter or the rest of Team Avatar's children like SOKKA'S FAMILY!