I understand Mannu's anger at not even being told he had a different biological father. He met Ratan in his dying moments which robbed him of a chance to get to know him, spend time with him and enjoy the child-parent bond.
But there is no way to justify Mannu's current actions. However hurt he is by his mother hiding the truth,should he not pause to think even once whether she had some reason to do it?
Should he not ask himself if there is another version of the story? He has been shown so far as a very mature, responsible adolescent, and so the least that was expected of him was that after the initial hurt , he would weigh both sides of story, and get a grip on his anger and life.
If he looked back at his life, he would see a loving mother, a devoted father and a doting grandmother . He would realize that he never felt discriminated against by his foster family. He would realize that he never for a moment felt they were not his own.
If Mannu's father was a step father in the way he now imagines him to be, surely the step-father wouldn't have been so affectionate towards him?
Ganga was subjected to unimaginable domestic violence by Ratan, and even given that he had changed, her fears are understandable.
It has been argued here that Mannu should have been allowed to freely meet his father. What if Ratan felt tempted to claim him? Which sane mother would want her child to be influenced by the kind of household that, even if in the past, killed, raped and tortured women?
Which woman/mother would so easily forget her horrific, dark past? Ganga was battered and left to die, and she is alive today only because Jagya rescued her and he was a doctor.
That one act saved Mannu too. Instead of growing up motherless in the home of a murderer, he grew up in the warmest, kindest household any child can get.. So much so he never realized, until the Ratan truth was revealed to him, that he was not originally part of BH. There is simply no justification for repaying the same family with unkindness and betrayal.