Bg 1.41

sankaro narakayaiva
kula-ghnanam kulasya ca
patanti pitaro hy esam
lupta-pindodaka-kriyah

Word for word: 
sankarah — such unwanted children; narakaya — make for hellish life; eva — certainly; kula-ghnanam — for those who are killers of the family; kulasya — for the family; ca — also; patanti — fall down; pitarah — forefathers; hi — certainly; esam — of them; lupta — stopped; pinda — of offerings of food; udaka — and water; kriyah — performances.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
An increase of unwanted population certainly causes hellish life both for the family and for those who destroy the family tradition. The ancestors of such corrupt families fall down, because the performances for offering them food and water are entirely stopped.

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
According to the rules and regulations of fruitive activities, there is a need to offer periodical food and water to the forefathers of the family. This offering is performed by worship of Visnu, because eating the remnants of food offered to Visnu can deliver one from all kinds of sinful reactions. Sometimes the forefathers may be suffering from various types of sinful reactions, and sometimes some of them cannot even acquire a gross material body and are forced to remain in subtle bodies as ghosts. Thus, when remnants of prasadam food are offered to forefathers by descendants, the forefathers are released from ghostly or other kinds of miserable life. Such help rendered to forefathers is a family tradition, and those who are not in devotional life are required to perform such rituals. One who is engaged in the devotional life is not required to perform such actions. Simply by performing devotional service, one can deliver hundreds and thousands of forefathers from all kinds of misery. It is stated in the Bhagavatam (11.5.41):

devarsi-bhutapta-nrnam pitrnam
na kinkaro nayam rni ca rajan
sarvatmana yah saranam saranyam
gato mukundam parihrtya kartam

“Anyone who has taken shelter of the lotus feet of Mukunda, the giver of liberation, giving up all kinds of obligation, and has taken to the path in all seriousness, owes neither duties nor obligations to the demigods, sages, general living entities, family members, humankind or forefathers.” Such obligations are automatically fulfilled by performance of devotional service to the Supreme Personality of Godhead.