Pitru Dosh is affliction arises due to not getting Nirvana to soul of departed forefathers. It mainly occurs when dead forefathers and ancestors did not get peace or salvation (Moksha) at the time of departing their souls. In Hindu mythology, it is believed that if anyone in the family do not offer water and food to their dead ancestors, in shradh. It is believed that soul of your ancestors or departed forefathers earnestly search for Moskha, if their death was unnatural or occurred at their early age. Due to premature death, their souls do not get Nirvana and wander on earth aimlessly.