I was thinking about Birth By Sleep, particularly Ventus and Vanitas.

Ventus' heart has been split practically a billion times.

First his original heart was made by Sora (I need citation on this actually, I haven't seen anybody mention it recently) So already he doesn't have a complete heart. Then his heart gets split to form Vanitas. Now he has roughly a quarter of a heart. Then he loses his heart, and ends up in Sora. Sora loses his heart and Ventus' is split over Namine and Roxas. What's more, Roxas, Namine and Xion all have parts of Kairi and Sora mixed in as well.

So basically Ventus' heart has been diluted to 1/96

Crazy.

i know right? But Namine isn't from Sora. She's from Kairi

You have a point there but i thought that Xehanort split up the light and darkness in Ven to make Vanitas. Then Ven went in comatose state and Sora awoke him. But the rest is correct i think.(not sure about all of this so if im wrong please tell me)

And Ventus_XIII, hatok was kind of correct and you are too but Namine IS Kairi's nobody but it is her nobody through the heart of Sora(Namine was created when Sora released Kairi's heart from his own.)

I was thinking about Birth By Sleep, particularly Ventus and Vanitas.

Ventus' heart has been split practically a billion times.

First his original heart was made by Sora (I need citation on this actually, I haven't seen anybody mention it recently) So already he doesn't have a complete heart. Then his heart gets split to form Vanitas. Now he has roughly a quarter of a heart. Then he loses his heart, and ends up in Sora. Sora loses his heart and Ventus' is split over Namine and Roxas. What's more, Roxas, Namine and Xion all have parts of Kairi and Sora mixed in as well.

So basically Ventus' heart has been diluted to 1/96

Crazy.

 

It wasn't. Ven's original heart was his own.

Then his heart is split to create Vanitas. Looking at the first cutscene when Ven is having the conversation with Sora's heart, it looks like Vanitas took up about 1/3 of his heart.

Then he merges his heart with Sora at the end of BBS.

Sora stabs himself with the Heart Unlocker and then Ven's heart, unable to return to his body, remains in Sora's body and goes on to become Roxas. It's debatable whether it merged with Sora's heart completely when Roxas merged, or is still separated and merely using Sora's body as shelter.

... through the heart of Sora...

The other way round: She was made from Kairi's heart and Sora's body.