I have a question....
Jai was really scared of Bani finding out about the Raaz, because he felt that she would never forgive him or would leave him because of it. Why would she leave him???
The whole situation is very sad, and I can see that everyone involved would be sad.... But, in the end, we all have to remember that it was an accident.
1) He didn't go out for the purpose of killing Bani's mom... and he did take Karin (Bani's mother) to the hospital to try to save her.
2) He also gave Bani's father money to try to help ease the situation (and yes, I know that money can't replace a loved one) but he didn't do it on purpose.
He was wrong for not telling her in the beginning, but he isn't at fault for killing. It was an accident. Anyways, this is only my oppinion....