My question is not what is pitra dosha? That I already know. My question is pitra dosh is person specific or affected to whole lineage of person? Is it genetic decease which a person inherit from ancestors or is it kundali specific caused by sin in pastlife?
No dosha is permanent , be it in any lineage. But, if a person is born is a lineage with dosha and inherits the dosha, then understand it as manifestation of his own sins done in previous lives. It is like sending a criminal to a prison where already guilty persons are present having done similar crimes. Please do not think that an innocent person will inherit a dosha only because he is born somewhere. SrimadBhagwadGita- jiva apne hi karmon se bandha hai. It is not kundali which is cause of one's good or bad, it is karma of previous lives and present. The kundli mere reflects it so that remedial actions can be taken.
In the chart, the Sun is the significator of Pitr (manes). So this dosha is generally formed when Sun is significantly afflicted in the chart. However, it is not evil as portrayed by some of the astrologers which frightens common people. Usually if Sun is afflicted by enemy planets like Rahu or Ketu this can be a factor.
The best remedies is to perform regular tarpanam on every amavasya and do some charity to the poor and/or feed stray animals/birds.
Regular chanting of gayatri or an anushthan is extremely helpful.
One must try to offer pinda by visiting places like Gaya or any other pilgrim place.
Regularly watering plant is also beneficial. Planting new saplings is also very good.