Bhisma vowed sacrificing his crown prince title.

Shantau and River Ganga in human form.Shantanu asked Ganga to marry him.She gave birth Devratha who was later known Bhisma



Shantanu took Devavrata to his kingdom and crowned him as the prince, the heir apparent.

One day when Shantanu was wandering on the banks of the river Yamuna he met a beautiful girl and fell in love with her. Her name is Satyavathi.He asked her to marry him. She said, 'please ask my father and get his consent.' The father was a fisherman. He refused on the ground that his daugher's children would never become the ruler after Shantanu as he had already a son. It was a price that could not be thought without shame. Shantanu was therefore unable to give his word on accession, as it would be unfair to Bhisma, the rightful heir to the throne.

He returned to his capital. He could not forget Satyavathi. On knowing the fact from his father Devavrata went to the father of Satyavathi and took a terrible vow, sacrificing the crown prince title. He vowed that he would never marry. At this fisherman praised Devavrata and agreed for the marriage of his daughter Satyavathi to the King Shantanu. The gods showered flowers on Devavrata and uttered 'Bhisma'. Bhisma means one who undertakes terrible vow and fulfill it.

Chithrangada and vichitravirya were the two sons born to Shantanu and Satyavathi.