Here is an old saying -
Poot kapoot to kyon dhan sanchay
Poot sapoot to kyon dhan sanchay
It is true, if the son is bad an unworthy then why save wealth, and if the son is good and worthy then why save wealth. In this KK scenario it would have been apt if they had asked their sons to earn their living on their own. Let them face the harsh realities of life and learn the lesson hard way, then might be the situation would have been different. Both their sons being kapoot are fighting over the wealth earned by their father and hurting the sentiments of the old couple.