Kya is the second of Avatar Aang and Katara's three children and their only daughter, as well as the couple's only waterbending child. After traveling the world and becoming a renowned healer of her own accord, she settled down with her mother in the Southern Water Tribe following Aang's passing, though frequently travels to Republic City to help out whenever the city is in trouble.

Btw, Kya is canonically a lesbian. She is the daughter of Aang and Katara and is shown to have romantic interests in women, with her sexuality being a point of discussion in the series. 

Google it if you don't believe me.