Custody of child if mother is death and father does not want her

Sir, my younger brother had a baby girl last month and unfortunately his wife passed away after 48 hours of giving birth. the hospital issued a death certificate stating death due to sepsis and multiple organ failure. Now his in laws were unfairly accusing him responsible and forced for an autopsy. the post mortem was done within 24 hours and reports are still due. His in laws are now torturing him mentally with baseless allegations and wanting the baby girl. they are planning to claim money against the hospital and even want to use the baby to ask compensation.which he is against of but they are emotionally blackmailing to file a case of harassment against him and his parents and threat to take the baby away. I want to know whether they have any custodial right to do so and if death due to sepsis is something to fight against the hospital? does it count for medical negligence? Does the father has the sole right to give the baby for adoption to Me who is the paternal uncle of the baby?