If Aang was an airbender and Katara was a waterbender, then how come Bumi has no bending elements at all? I mean you would think that Bumi would have some kind of element, seeing that Aang was the avatar! When Pema and Tenzin had children they all took after their father taking in his airbending. And Kya (Katara's daughter) has waterbending in her genes. I really don't get it.
There is no rhyme or reason as to how the genes for bending are passed along. In the example of a water bender and an air bender, the possibility still exists that:
- You could be a water bender like your mother,
- You could be an air bender like your father (most likely due to the spiritual attainment of air benders),
- You could have no bending capability at all like your uncle (Sokka),
- In the case of air-benders, they always tend to breed true due to a spiritual attainment. Air-benders tend to beget new air-benders. However, this does not mean they could also have children who did not have the power to bend at all.
- Since the power does not move in a standard genetic process, there is no way to be 100% sure how anyone's children's bending capacities might no matter who their parents were.
It turns out that
He actually can airbend Click here
If you think about it, it makes sense. Katara was the only one in her family that was a waterbender if I recall correctly, meaning that it was a recessive gene in Katara's case. If that's the case, then Bumi ended up inheriting nonbender genes from both Aang and Katara.
It wasn't until after harmonic gate opening up that Aang's air bending genes ended up being dominant, causing Bumi to become an air vender later on as the story went on.
Well bending isn't 100% genetics, but it does pass through family lines, Katara was a waterbender while her mom and dad weren't, someone in her family was though I'm sure. Well all born air nomad was a bender. But since katara had non benders there was at least a 90 percent chance of a bender for a child.