The Vasu Dyu steals Vasishtha's cow and is born as Bhishma
Dyu, one of the eight Vasus, steals the cow Nandini for his wife; Vasishtha curses the Vasus to human birth and Dyu to a full life on earth as Bhishma.
Ganga, about to leave Shantanu, explains the eight drowned sons. The Vasus were walking with their wives near Vasishtha's hermitage on Meru. Dyu's wife wanted the cow Nandini for her friend Jitavati, daughter of Ushinara, so that she would never age. Dyu stole cow and calf with his brothers' help. Vasishtha saw it by ascetic vision and cursed them to human birth; when they pleaded he freed seven within a year but kept Dyu on earth for a long life, virtuous and childless. Ganga takes the eighth child away and later returns him grown, as Devavrata.
Ganga, leaving Brahma's court, meets the dejected Vasus on the road. They say Vasishtha cursed them for a small fault: he sat at his twilight prayers, they did not see him and crossed him. They ask her to be their mother, name Shantanu as father and ask to be thrown into the water at birth. She asks that one son may live; each Vasu gives an eighth part of his energy to make that son, who will be childless.
What is different here:
No cow, no wife, no single culprit: all eight offend alike by crossing the sage unseen at twilight. The surviving son is made of an eighth of each Vasu, not Dyu alone.
The Purana repeats the cow story with the same names: the Vasu Dyau, his wife, her friend the daughter of Ushinara, Vasishtha's search and curse. It then tells Ganga's marriage; here Shantanu falls at Ganga's feet to beg for the eighth child's life.
What is different here:
Follows the Adi Parva 99 version closely; adds the king's plea at Ganga's feet and frames the whole within praise of the Goddess.