Bhishma Pitamah is the grandsire in the Mahabharata. The
story of the birth of Bhishma Pitamah is found in the Adi Parva of the
Mahabharata. He is the son of Ganga and King Shantanu.
Ganga had married King Shantanu on one condition that he
will never question her actions. If ever he questioned her action, she would
leave him forever.
They led a happy life but things changed with the birth of
the first child.
Ganga mercilessly drowned the first seven children she had
with King Shantanu.
But on the birth of the eighth child, Shantanu could no
longer keep silent and he forcibly stopped Ganga from drowning the infant.
Ganga told the king that he had broken the promise and it is
time for her to leave him.
She told him that the seven children she had drowned were
Vasus. The eight Vasus were immortal but were cursed to be born as mortals on
earth. They took the help of Ganga to make their stay on earth as brief as
possible. That is the reason why she drowned the seven infants.
The eighth Vasu will now have to live a very long life on
earth.
This child was named Devavrata.
Ganga took him with her and got him trained by Sage
Parashurama.
When he came of age, Ganga sent him back to his father
Shantanu.
When he took the terrible vow that he would never marry and
he would never become the king of Hastinapur, the Devas called him Bhishma.
Bhishma means the one who takes the most terrible vows.