[orpheus2]

I formulated this theory under the assumption SAO and Accel are indeed in the same timeline and what little knowledge I have regarding both.

Spoiler for Theory:

It was proven back at the light novel thread that KYH is not Kirito's child. After all, Kirito and Asuna won't be such neglectful parents. But what if, they were but not alive. Essentially, KYH and her sister were taken in by relative of Asuna. Thus explaining, why KYH is well off. The reason of death of the original parents was because of an accident or related to GGO gunman case.

We have seen AI in Accel World in the form Ash Roller. There some evidence that Kayaba is now a digital entity given what happened at the end of ALO. It could be that Accel World is a creation of Kayaba in order make a new successor for his Seed since Kirito died. If remeber correctly, the reason why Kirito was exceptional was because of his reaction speed. So Accel World has two purposes: Experiment and Seed successor.