Okay, this is a theory that I’ve been playing with and have discussed with a few of my friends.
First lets go back to Avatar: The Last Airbender, Book 2: Earth season finale:
Azula being as crazy as she is shot Aang in the back WHILE he was in the Avatar state and stated by Avatar Roku in the first episode of Book 2:
"If you are killed in the Avatar state, the re-incarnation cycle will be broken and the Avatar will cease to exist"
But as we all know Aang is alive because Katara revived him with the sacred water.
Now think, he did died in the Avatar State, but came back, but the time he was gone could have messed up the re-incarnation cycle and this is how we get Amon.
Amon says he was born to non-benders and is a non-bender himself, but I don’t think thats the case. The non-bender parents is okay, I could believe that, but him being a non-bender, no.
I think he’s Korra’s missing half, she has the fighting side of bending and 3 of the elements so far, but has yet to even touch air and the spiritual side of bending. I feel that Amon has this side of the bending, he has air and the spiritual side and that when Aang died the cycle split into two different people. This is why he can “take” bending, but we’ll get to that later. Also, his fighting style is very passive defensive like an air bender, because air benders have a passive aggressive style, it’s more defense then fight. And in the episode 9 “Out of the Past” if you look at when Amon jumps through the cloud of snow, it looks like it swirls like he was airbending. (Don’t pay attention to the “let me love you”, please)
So my conclusion on Amon is that he is the other half of Korra, an Air bender and has the spiritual side of the Avatar and this is because Aang died and was revived messing up the Avatar cycle.
Now on to Amon taking bending away…
Back to Avatar: The Last Airbender, Book 2, episode “The Guru” Aang is opening his chakras and during the episode the guru states:
"The sixth pool of energy is the light chakra, located in the center of the forhead. It deals with insight and is block by illusion. The greatest illusion of this world is the illusion of separation."
Now look at where Amon places his hands.
One finger at the center of the forehead and I believe a finger at where the “amon” body part that is located on the back of the neck.
Now Aang’s hand placement.
At the center of the forehead and the heart, he learned from the Lion/Turtle island. He was a full Avatar at this time and the time he took Fire Lord’s bending.
So Amon might just be creating an illusion of having your bending taken away and no matter how hard you try to bend, the illusion of separation is stronger then your insight.
Also, he could be still half of Korra and the rest he can only create the illusion of taking bending is because he is not a FULL Avatar and can’t take bending away because he is not whole and this also applies to Korra as well if she tries to restore peoples bending.
Now the age difference, I think Amon is about 25-35 so Aang had not passed away yet and is still kicking, well like I said earlier, the re-incarnation cycle could be messed up and Amon could have been born while Aang was alive and then when Aang passed away Korra was born.
Now think of this, what if when Aang passed on, Amon’s bending ability show itself and his parents tried to harm him or he could have killed them and that’s why he hates bending so much is because his first experience cost him peoples lives, so he’s learned to harness his abilities and possibly looked back at the passed Avatars, since he would have the spiritual side and learned how to “block” or “create the illusion” of your bending being taken.
When he learned about Korra being the Avatar, he probably figured out that he is the other half of her or again the passed lives could have informed him that he and Korra are incomplete and instead of taking her bending he’s going to absorb it and become the Avatar or Korra will go into Avatar state and absorb his abilities.
Which brings me to another point, I also think that Amon can absorb peoples bending, I mean if your the Avatar why couldn’t you absorb peoples bending, because in the finale promo it kinda looks like Amon is bloodbending Korra and Mako. Which also could explain why he could resist Tarlock’s bloodbending from my earlier explanation, of Aang being alive while Amon was born, Amon could have kind of absorb some of Aang’s (I don’t know, memories or something, think of Naruto clones, when they learn something then puff back into Naruto he sees and instantly learns what they did) and that’s why he could resist, because Yakone’s )<—spelling) bending got taken away by Aang and you have to think where does the ability to bend go, I think it goes into the Avatar, at least somewhere into the mind or body.
So there you have it, my theory and if you don’t like it, well it is my opinion and you don’t have to like it, but it’s interesting to I think and I’d love to here what you guys have to say about it.