Author's Note: I do not own Bleach or its characters. This is wildly AU.
And All For the Want of a Horseshoe Nail
Aizen had not planned for Gin's betrayal due to Rangiku's pregnancy. This was evident on his face when Gin explained things to him. Of course, this was after Gin had stabbed him in the chest, so Aizen wasn't exactly at his best and the expression might have something to do with that. He certainly hadn't been ready for this twist of events. Then again, he hadn't known that his own plans had been hijacked. In the end, their strategy had really been to give Aizen enough rope to hang himself with.
Kyoraku and Ukitake had done a good job of planning in order to minimize the damage Aizen did in with his departure, and Gin had enjoyed pulling the wool over both Tousen and Aizen's eyes. Some of the actors in the play hadn't been informed of their parts until afterward, and not everyone informed (before or after) had taken things well. Hinamori had been devastated to find out that her beloved Captain Aizen was using her, though Rangiku had said Hitsugaya was taking good care of her, and it was better that she had found out through Yamamoto rather than being stabbed by Aizen.
He had gone with Aizen and Tousen as spy and secret weapon. Really, it had been quite fun for Gin. Hueco Mundo was not really a place for children, but it did afford Gin a chance to get a feel for the Seireitei's enemies and mess with their minds a little. He regretted having to miss part of Rangiku's pregnancy, but the Shinigami Women's Association would take care of her, and someone had to make sure that their plans to deal with Aizen went through. But really, Gin was glad that it was all over now.
Several months after the end of what had been termed the "Winter War", Rangiku Matsumoto went into labor. A full month before her due date. After nearly twenty hours of labor and three broken fingers on Gin's part, Captain Unohana delivered two healthy babies. The woman smiled at them as Isane handed Rangiku and Gin each a blanket wrapped bundle.
"Congratulations. You have a pair of perfectly healthy twin daughters."
Isane had to snatch one of the babies back up as Gin fainted.