Bhishma, born as Devavrata, was the eighth son of Ganga and King Shantanu and was the legal heir to the throne of Kuru dynasty. Ganga left Shantanu after the birth of Devavrata. King Shantanu eventually fell in love with a fisher woman named Satyavathi and wished to marry her. When King Shantanu approached Satyavathi’s father for her hand , he denied claiming that when Devavrata takes the throne Satyavathi and the children born to her will end up as slaves of Devavrata. Shantanu could not agree to this conditions and fell into deep sorrow.

Understanding his father’s predicament, Devavrata met Satyavathi and her father and to get the consent for the marriage he took a vow that he will never have the throne and will remain a Brahamachari ( will follow celibacy) life long. He also promised that his entire life will be dedicated to serve the throne of Kuru dynasty. Seeing that his daughter and her offspring will have the right to the throne Satyavathi’s father agreed for the marriage .