Bill killed O-Ren's father

Did you know that Bill killed O-Ren's father,
In the story of O-Ren life, in the scene that O-Ren's parents died, after O-Ren's father was killed by the Samurai Sword and when they showed us his killer it was Bill when he was younger, because of the rings and The Hattori Hanzo Sword.

I believe this has been talked about. Check here for at least some of the conversations. Here

Wow I did not even know that.

Thats just wrong and cool at the same time.

I realized those two fast the first time I seen it..