A person's destiny is fixed by number of breath, hence our Yoga is all about breath control and the way forward to increase longevity. More food in stomach more oxygen required through breathing, so person likely to die before his age !
A human being has family, takes birth within a community, community lives in a society, society lives in a state then country....etc.. All of them collectively contribute to the good or bad karma and this in turn may increase or decrease the life span.
Bhagirath did penance and brought mother Ganga to earth and also brought salvation to all his ancestors, who were "burnt to ashes", there getting blessing from "pitrus" and also longevity.
It is in recorded history that Mughal emperor prayed for his son Akbar's life in return Babar himself expired shortly afterwards, while Akbar survived to rule till his old age... Akbar with no options gave away his kingdom to the spoilt kid Humayun of anarkali fame.
There are many instances in recorded history, where parents prayed and increased children's longevity and vice-versa.
Those knowledge in jyotisha sastra would be able to throw much more light with evidences. Prayers help in increasing longevity (Mahamrityunjaya mantra).
The elder brothers of Lord Krishna for various other known reasons, had to die in hands of his Uncle Kamsa i.e. brought sorrow to their parents (Devaki-Vasudeva), whereas Lord Krishna brought relief, release, ananda & moksha to his parents.
Children born during month of April, when planet Sun is exalted is likely to give longevity to parents, while births in October, when Sun is debilitated may reduce longevity
That is why in India, there are certain beliefs on children born during amavasya, purnima (mother's longevity issues), eclipse period (lunar / solar), lunar = mother longevity, solar -father's longevity. This has astrological basis and astrology is one of the limbs of Vedas.
In short, family, community, society, state & country shall determine the fate of an individual, at the same time living style, individual karma & family/ parents karma also contribute to longevity.