It's quite clear that Kamal and Swaran comprehend their sons' demeanor in their separate monologues or scenes in their sensitive situation. While Swaran noticed Yug and Vikram are acting frivolous towards their father's present scenario, Kamal already was cognizable of Nakul subconsciously allowing Kiran to manipulate over the matters by avoiding Kamal and Swaran's foot onto the USA soil or going back to India (hence Nakul being pingponged between wife and parents).
I adore the parenting moments between the Swaran, Kamal and the three kids in their childhood but I felt this image of "typical perfect & happy family" resulted in cracks as years passed into the kids' adulthood age.
Today, Kamal revealed a backstory about their sons demanding for their share & labeling him as a thief. (There have been mentions of a 4th son but not sure what the story behind this character. Even Swaran's friend mentioned of the 4th son but not sure of the entire context at this point.) I think he already sensed a drifting of Nakul when Kiran entered the family, but this moment took the limelight of the sons becoming selfish for their means. I just feel somewhere the parenting was a failure by overpampering the three children beyond what was required.
When Swaran questioned over buying a new bicycle for Yug, I feel that was moment was a bit of a catalyst for Vikram's transformation somewhere.
(Asking parents for money in terms of obtaining education is okay but constantly asking for money was jarring; just made them steer away from performing tasks individually).
The fourth son is not a character it's the house they were talking about that it's like her fourth son so he would never sell it
