Ooooh dear, if Fai WAS responsible in part for Kuro's mother's death, things would just be *too* messed up. Their relationship is already pretty screwed up right now, haha.
So, hmmm. What we know of Fai is that he sealed Ashura because it was "all he could do", he thinks Ashura will persue him when he wakes up, that Ashura "took him with him" somewhere, and possibly that Fai was a captive or "instrument of imprisonment".
Ah, yes. And there's the speech Fai had in the Clover bar. The scans I have translate it as him saying "I've been waiting... for someone who can stay by my side" (not sure who to credit for that one) whereas Del Rey translated it as "I was a guy who always waited for the one who would take me along".
Siiiiiigh. My brain is fried trying to figure this one out.