User blog comment:Warya123456/Is Aizen really dead?/@comment-1769234-20100802091147

Maybe Gin knew he couldnt kill Aizen at first and needed to find a way to do that and by working for him he found that weakness.

Side note I think Gin want to be a being of pure source of death and Chaos and that he need Aizen out of the way to make it.

After all said by aizen himself to Shinj the betrayal yu can see is trivial the ones you cannot see if what truly is frightful.