This is one of the most important concepts of Indian astrology and it is called Pitra Dosh which is generally defined by many astrologers as the Curse of Ancestors meaning that the forefathers of the person having Pitra Dosh in his horoscope are unhappy with him and therefore they are cursing the native and due to that curse the native may suffer from debt, diseases, failures all around, being childless and in the worst cases early death due to accidents or serious diseases, Kaal Sarp Dosh, Mula Dosh and Manglik Dosh among other defects. And in case of Pitra Dosh, the misconception starts right from its definition which states that it is the curse of Ancestors.
A Pitra Dosh is not the curse of ancestors or forefathers. It is a Karmic Debt of the ancestors, and is to be paid by the person having Pitra Dosh in his horoscope. In simple words, a Pitra Dosh is formed in the horoscope of a person, when his/her forefathers have committed some mistakes, crimes or sins. So in return, this person is supposed to pay the Karmic debt by going through different punishments decided for those debts in different spheres of his life. He has to go through this until the debt is cleared either by taking the punishment or by doing good deeds.
I mean if a person grows older and does some bad Karmas or Bad deeds which may bring disgrace to the good and fair name of Ancestors, and then it may be considered that the Ancestors are cursing that person.
Pitra are our own ancestors' who have been thrown into pretha yoni or any other lokas and as a result of this they become extremely restless and sad and expect to get mukti from that state through the karma of their successors they are considered to be more important to a person than any other devthaas (excluding sadguru) as they will be having blood relationship with their successors .they are consider unequal to gods. As this body ours has come into existence because of our anscestors ,pitradosha nivarann is considered to be a very important duty of a person. If the pitras are satisfied and happy with our shradd (actions offered with shraddha) they can bring joy and clear our path to success in all spheres. There are many rituals of pitra dosha nivarann.