Smt. RR,
The issue of "pitru sApam" or "pitru dosham" is a commonly accepted one among the Kerala astrologers and the average Keralite also. I am not however sure whether the word "pitru" here denotes our ancestry/lineage only or something else also. For example, one of my friends consulted an astrologer about the delay in his son's marriage and he was told that the said son has pitrusApam from his mother's side and so a normal marriage would be next to impossible. That boy got married above the age of 30 to a girl from another caste.
There is another case of a person who is now over 53 years. He was a very bright student and cleared his first year M.A. in sanskrit with flying colours. But then a kind of OCB caught hold of him and for nearly 30 years now he spends most of his waking time in the bathroom continuously washing his hands and legs! One Namboodiri jyotsyan had predicted, when this change had set in, that this boy had very strong pitru sApam and he would not be normal and that only very experienced Tantriks would be able to correct his behaviour. His maternal uncle, a reputed doctor in allopathy, gave him psychological treatment and medicines for some time but there was hardly any improvement. Then his father took the young man to Bhuvaneswari Swamigal who did some elaborate homam and poojas but even those did not have any beneficial effect.
One old and very austere tabra (who died more than 20 yeas ago, after retiring as a very powerful official under the regime of the Travancore Maharaja) and was a close friend of the then Sringeri Acharya,and other religious people, developed a "kink" which made him "see" worms in his food. Being a very austere person he had to go practically without food, so to say, for a long time. The astrologer then said that it was due to pitru sApam and that there was no remedy for that.
I myself don't know whether pitrus will curse or trouble us, the humans living here. But there is one mantra in our Tarpana which goes as under:
उद् ईरतां अवर उत्परास उन्मध्यमाः पितरः सोम्यासः ।
असुं य ईयुरवृका ऋतज्ञास्तेनोऽवन्तु पितरो हवेषु ॥ ऋग्वेद 10-15-1
ud īratāṃ avara utparāsa unmadhyamāḥ pitaraḥ somyāsaḥ |
asuṃ ya īyuravṛkā ṛtajñāsteno:'vantu pitaro haveṣu || ṛgveda 10-15-1
Here one's pitrus are classified into three categories, the best, the mediocre and the lowly. This ṛk also prays to (all of them) to be "avṛkā" (lit. not wolf-like) that is not to cause harm to the person praying. Since all hindus including the vaishnavites accept "the Vedas as the ultimate pramaanam (unassailable truth)", (
see here), I think we hindus ought to accept the fact that the pitrus may cause harm to any one of us or, may be, it is only a manner of describing some kind of prārabdha/sancita karma of a person, just as TB was referred to as राजयक्ष्मा (rājayakṣmā) in our ancient literature.
Whatever the case be, there are some horoscopes which show pitru sApam/pitru dosham and I have found in my experience that there is no parihaaram for this. It is quite possible that nowadays the Nadi jyosyars and other astrologers have a "nexus" with some temples and/or vadhyars and make money from this, but so far, in my surroundings no astrologer has said that pitrudosham can be remedied by parihaarams; one has to experience its results, that is all.
(Of course, vaishnavites may find solace in the belief that Narayana will undo all such defects if a person does "prapatti" but it is finally a matter of personal or group belief; we humans cannot know the truth whether Narayana really exists, whether he is capable of pardoning and erazing all sins from a human who has done the prapatti or samaasrayanam, etc., and we have only second person statements in support of such beliefs.
May be people adversely affected by pitrusaapams can convert themselves into vaishnavites!