The park road accident has been highlighted many times. We know it involves Jai, Roshni and indirectly Bani. That means a strong connection between Jai, Roshni and Bani's parents. Someone suggested that Jai & Roshni might have killed Bani's mum in the accident a long time ago.
Now, let's go way back to the 1st episode of Kasamh Se. After Bani's father died, she found a letter from her dad which says that she should take her sisters and seek help from Jai Walia. Why is this so? Is this because Jai Walia is forever indebted to Bani's family for having a hand in the death of Bani's mum? I really think Long ago when Jai and Roshni caused the accident, he promised Bani's father that he'd do anything to sort of 'repay' him back. So that's why he accepted all 3 sisters even though he didnt really like it. Plus, Jigyasa never can understand why Jai would want to do charity case to 3 unknown sisters. However, Roshni has ever mentioned that she knows Bani's mum had diabetes and Jai knew that Bani's dad was an alcoholic. How would Jai and Roshni know so much unless they had a long and deep history between themselves and Bani's parents..
However, I still cannot explain how the cheque with Bani's dad's name was found in Roshni's room.. Anyone can explain that?