Tenzin

Tenzin is an Airbender and son of the late Avatar Aang and Katara. Very little information has been gathered about his character, though it is known that the current Avatar, Korra, is seeking his tutelage in Republic City. He will be featured in the upcoming spin-off series, Avatar: Legend of Korra.

Background
Tenzin was born sometime after The War to the Air Nomad Avatar, Aang, and the Waterbender, Katara. At some point in his life, Tenzin was taught the ways of the Air Nomads and is presumably an Airbender, because the new Avatar, Korra is searching for his help in the crime-ridden Republic City, so she may learn Airbending.

Rumors & Speculation
These storyline elements remain unconfirmed.
 * In theory, Korra is the spiritual parent of Tenzin, seeing as how she is the new Avatar, thus being Aang in a previous life. This kind of relationship would be similar to the relationship between Zuko, Azula, Ursa and Avatar Roku.
 * It can be presumed that following Tenzin's birth, Aang was no longer the last Airbender.
 * It is currently unclear if Tenzin will be the only living Airbender in Avatar: Legend of Korra. He is so far the only one who has been confirmed. However, the possibility of Aang and Katara having other descendants, also potential Airbenders, has not been ruled out.
 * The marrying age in the Avatar World, at least within the Water Tribe, is 16 (presumably for both parties). Thus, as the series is set 75 years after Avatar: The Last Airbender, with Aang having died sometime between 156 and 159 ASC, Tenzin's maximum possible age is either 71 or 72.
 * Tenzin being 71 at the oldest seems more likely as Aang was only 12 years old (biologically) at the start of the first series and only 9 months worth of time is clearly shown to have passed during Aang's journey, as both solstices occur within the show.
 * Tenzin's minimum age is much harder to estimate, though the lowest that seems plausible is 41.
 * However, this would mean that Katara would have given birth to Tenzin at the age of 51, which is the average age most women start menopause. Thus, it is likely that he is older.
 * He may know relatives of Aang's friends.

Trivia

 * Tenzin is the first canonical interracial child ever mentioned in the franchise.
 * Tenzin's name is possibly derived from the 14th Dalai Lama, Tenzin Gyatso, also the inspiration for Monk Gyatso. This makes it possible that Air Nomad monks were referred to by their last names. This means that Monk Gyatso's full name might have been Tenzin Gyatso, which makes it possible that Tenzin is named after Aang's beloved mentor, guardian and father figure.

Relatives

 * Aang (Father)
 * Katara (Mother)
 * Sokka (Uncle)
 * Hakoda (Grandfather)
 * Kya (Grandmother)
 * Kanna (Great-Grandmother)
 * Pakku (Stepgreat-Grandfather)
 * Korra (Reincarnation of Aang, his father)