The term “pitru” means Father, pitru dosha means a dosha which is caused due to neglecting of duties related to lineage of father. There is a great importance to performance of shodasha samskaras (16 samskaras) right from the birth to death in hindus. We do pitri tarpana on death tithi of our ancestors or on sarvapitri amavasya which comes once in a year before diwali. The world of pitras is said to be passing closely to the earth during those 15 days. Pitru dosha is said to manifest as a result of curse of our pitras due to negligence of our duties towards them. Sometimes curses of pitras causes unending and unknown miseries in life, a person suffers inspite of having a very good horoscope and the cause is unknown. Lord hanuman did not know about his great powers before he was blessed with “Shri Rama”, Hanuman as a child was very mischievous and used to bring obstacles in tapasya of rishis on the account of which he was cursed by them that he will forget all his powers and live like and ordinary mortal. Hanuman had forgotten his powers until the time lord rama revived his powers by lifting the curse. So it is clear from the above story that a curse can hide your potential or create unknown obstacles and blessing of god or saints can remove it.
Pitru dosha is caused when Sun is afflicted by ketu/Rahu, Affliction of 9th and 2nd house in a horoscope also causes pitru dosha. Presence of rahu in these house can mean the wrath of pitras on the account of negligence of duties towards them or it could also be on the account of some of their wishes left unfulfilled, unnatural death of ancestors, such souls do not get emancipation and they create troubles and obstacles in your life, sun saturn conjuction in 5th, 9th or 2nd also indicate such troubles.
Some of the common problems caused due to pitru dosha are as follows :-
Rahu and ketu are the points in the heaven which cause eclipse to moon and sun respectively. The cause of sufferings caused by rahu and ketu cannot be detected, doctors find everything normal, yet the trouble is there. The sufferings caused by rahu and ketu are like them and cannot be detected but only experienced by the one who suffers, the reason is unknown. Pitru dosha creates same kind of miseries and sufferings the cause of which is unknown.
Often it has been observed that pitru dosha can be a cause for downfall in the horoscope inspite of everything being alright, unforeseen miseries and problems crop up from nowhere and create obstacles in the path of success. Workship of your kuldevi(family diety) and performing of pitri tarpana along with donation of food and water helps in begetting prosperity or success.