Rakesh was left with Naina when she was a new born. Considering the fact that he lived in a joint family and his younger brother having a child of the same age as Naina , its quiet Natural for Chachi to take care of the baby Naina along with Preethi. We never know she might have even breast fed Naina . This is very common in joint families when such tragedies strike. But all through out Rakesh has seen to that Naina is under his control. Her safety is something that he never meddles with. He is a rough character , even if his wife /Naina's mom was alive his approach to Naina would have been the same. If you look back he went for the trip ONLY because his daughter was there. When he realized that Naina got beatings from Kumudh teacher for something she had not done, he felt guilty as he had also questioned his daughter's intention, he then kept a hand on her head with affection. That simple gesture does show his emotions to his daughter. When ever Tayi ji taunts her , he has given it back to the lady. When Tayi hit Naina and she was hospitalized , he was very angry at Tayi ji. When he found Sameer in Naina s room at Mt. Abu he was furious like any father would be . He could have denied her being his daughter. Even during the present track he has always maintain that he is her father not even once has denied or refused to accept her as his daughter. True to the fact the might not have directly brought her up but he has seen to that she lives in a household where she gets enough happiness and care. And we need to remember Rakesh never remarried , he could have but he chose not to. Rather stay alone . Even with Arjun he isn't very affectionate. He feels bad because Arjun didn't come up in life , he feels he has failed as father there as well and hence his struggle to see Naina's life at least goes perfect.
Like any patriarch of an orthodox household , he feels Naina can be happy only by being married off into a family similar to theirs. This is called playing safe and he feels his younger brother s broadminded thoughts wouldn't work in a society like ours. Hence his anger against Anand and the reason for him to blindly listen to his elder brother and wife.
But Vishaka is a different person altogether. We have not even once seen Vishaka standing by Sameer. She is always hiding her affection. She is educated comes from a rich family. Even then she refused the responsibility of a child that she gave birth to. Instead she preferred to keep her other family happy. She is much better placed than Rakesh in life, but sadly she doesn't have the guts to accept Sameer whole heartedly. For her class and status matters. She refused to accept him as her own son at Mt. Abu. Whenever Sameer was in trouble she never stood by him nor did she find someone to stand by him. When there was problem in Delhi , she knew the cause was her mother in law, she sent Sameer away and not her MIL. She never questions her husband of being an incapable father for Sameer. Vishaka is a very weak character and sometimes I feel she is very selfish.
Vishaka's hatred for Naina is because Naina is everything that Vishaka isn't. Naina is one person that Sameer listens to...so basically Naina became the center of Sameer's life and Vishaka couldn't even touch the periphery of his life.