Different families

The Karmarkar and Malhotra families have so many similarities and differences but what is interesting is how the Karmarkar children (except Shivam and Vandana) turned out to be so bad yet the Malhotra children turned out to be good people. 

Both familes did not have mothers bringing them up. Malhotra's had a bad dad + a bad aunty. Karmarkar's had a good dad and a good aunty. 

How did the nurturing in these families produce such opposite results??

You’re right.

Sometimes I wonder if this is intentional to show what happens when you marry someone who is not the best person for you. Vijay and Vani probably should have married each other but they both had awful spouses. Now, this is the result. Both families are a dysfunctional.

I think Vani is trying hard to change this narrative by getting Kunal and Vandu closer together but I am not sure her efforts will be successful because Kunal is stubborn and mean.