Background :
There is little to be said about Data-7 background.

What I can tell is difference between the comic version and the animated version. Here is the story from the books.

In his origins, he was Cyber-29. He was Cybersix best friend and they played together when children. one day, they both went into the forest, escaping from their gardians. 29 wanted to make Cybersix climg into a tree to have fun. But as they were playing, a guard arrives and surprises them. The shock of being found made 29 looses his concentration and he simply felt on the ground killing himself.

The body of the little dead cyber was bought back at the castle and Von Reichter saw the opportunity to make an experience with Cyber-29's brain, using it in a black panther's body.

29 now in a different body, was tortured by Von Reichter, and became his slave, his pet. A killing machine obeying his master's commands. Many years later, when Data-7 saw the picture of his sister, memories attacked him and he attacked his master in fury. Then he fled in the forest and found Meridiana, where his sister was now living.

The story of the animated version of Cybersix differs in many ways, while keeping the same "storyline".

When they were young, 29 felt down a cliff while trying to get a flower for his sister. He died and his brain was again used to create Data-7. He became an allied of Von Reichter. When Cybersix was discovered to the eyes of Von Reichter once again, he decided to send Data-7 to kill her, a point which differs from the original sotry.

Data-7 sees the picture and has a flashback, but he still obeys his master. It is only later when he fights Cybersix that an old picture of them young, and the tatoo Cyber-6 on her sister's arms that he remembers who he really his, and who she is for him.

Data-7 his a definite important character in the the story. They are borther and sister and this huge bond makes them incrdible allies in the story. While in the comic, they love each other (as family I mean), they are not always together, or not as much as the animated serie shows to us. They will help each other in case of needs, but they do not depends on each other.

This aspect which was changed in the animated version of Cybersix, is ne of the best perspective of the serie. It is obvious they are closely binded together, and often they will go for the rescue of one or the other, often risking their lives for the sake of the other.