Kunal's behavior has so much to do with growing up in meenu's shadow.. you learn what parents do rather than what they say..So he has learned the mind games from the best.. he has never felt emotions or loved life like abir has done..and some of the reason behind it has been abir.. kunal had to grow responsible to fulfil abir's role for the family and office.. being sandwiched between abir and meenu and no one to talk to simply..
Abir knows that meenu manipulates kunal, but he has never just sat and talked to kunal about his feelings, his emotions and why he does whatever he does.. so agin I get kunal as well..he has grown up with deals and all..shweta was his first love and we all know what she did..in his own right, he tried to create a relation with mishti and then it all fell apart and no one's emotions and grievances were ever addressed in the show so all of them carry that as a baggage.. he liked kuhu but never thought of it as a real relationship in his purpose to save bhai from evil mishti and now when he is in this relationship, it suffocates him..