Yuuki Family in the Making

Jaden Yuki grew up thinking he was an only child.
However, what is the reason for his father and mother, Seto and Aiko Kaiba, to not be at the house when he was younger?
I'll let you in on a secret. When Jaden was three, his little sister, Yaya, was born. But that's not the only sister he has. His older sister, Asuna, was almost taken by another powerful company.
Seto was concerned for his children's safety and separated them, along with changing their last name to hide their identity.
Yaya was sent to Japan to study at Seiyo Academy with foster parents. Asuna also went to Japan and became the heir to a company that developed online gaming.
Jaden remained with Seto and Aiko, knowing in his heart that something was missing, but not having the courage to ask what. Until his thirteenth birthday, where in the two years leading up to his enrollment at Duel Academy, he was testing out a new kind of technology, NerveGear.....

(This is a Sword Art Online/Yu-Gi-Oh! GX/Shugo Chara crossover fic. I strongly recommend watching all three animes before reading this!)