it is karan and tanya's fault for the MOST part. doesn't matter if they live in a joint family the main responsibility for raising children is on the parents, every single other person comes second. karan and tanya always argue with each other instead of disciplining there kids, they each favor one child more over the other. they need to show a united front infront of there kids whether its a normal day or there disciplining there kids. they should save there fighting for when there alone.
However, no decent parent wants there kids to turn out badly, they do there best. raising kids isn't a science, you deal with situations as they come.
sometimes despite trying hard peoples kids don't turn out great and thats just fate (i don't mean it was meant to happen but despite the parents best efforts it just happens).
no parent wants there kid to turn out badly but sometimes that what happens.
karan and tanya are at fault period.