Everybody he’s originally related to is dead so I don’t know where you got that from. All I know about Aang we got from the series.
He was 12 when he saved the world. Made out with Katara a lot and helped Zuko found the United Republic. Brought peaceful ass balance to the world (ssshh, Yakone was like a 20 minute hiccup). Built Air Temple island, had loads of sex with Katara and they had 3 awesome kids; Kya, Bumi and Tenzin. Kept some more balance and then decided to call it a lifetime and popped off to the Spirit World. Turns up now and again to give Korra sepia coloured advice when she hits her head really hard.