In the backstory, Aang (Air Nomad) and Katara (Water Tribe) married and had three children. Tenzin was the only Airbender, while the other two children's bending abilities are unknown.
Tenzin himself married Pema, a non-bender (ethnicity unknown). So far, all of their children have been airbenders.
Mako (firebender) and Bolin (earthbender) are the result of a marriage between Fire Nation and Earth Kingdom citizens.
The trope is now known as Maligned Mixed Marriage. Was the couple's interracial relationship looked down upon in-universe?
TheOtherSteve
07:56:08 PM Dec 28th 2011 edited by TheOtherSteve
We honestly do not know. The show won't premiere until later 2012.