Mbh 5.147.3a

“Vasudeva said, ‘Hear, O king, the words that were addressed to king Suyodhana in the midst of the assembly of the Kurus, and, O king of kings, bear them in thy mind. After my words were ended, Dhritarashtra’s son laughed aloud. Highly incensed at this, Bhishma then said, “Hear, O Duryodhana, what I say for (the preservation of) our race, and having heard it, O tiger among kings, do what is beneficial to thy own house. O sire, O king, my father Santanu, was widely known in the world. I was, at first, his only son. A desire sprung up in his heart as to how he might obtain a second son, for the wise say that an only son is no son,--Let not my race be extinct, may my fame be spread. Even this was his desire. Knowing this to have been his desire, I procured Kali to become my mother, having myself made a promise highly difficult to observe, for the sake of my father as also for the sake of our race. How, in consequence of that promise I could not be king and have drawn up my vital seed, are, of course, well-known to thee. (I do not grieve for that). Observing that vow of mine, behold, I am living in happiness and joy. In her, O king, was born my younger brother, that mighty-armed and handsome supporter of Kuru’s race, viz., Vichitravirya of virtuous soul. After my father’s ascension to heaven, I installed Vichitravirya as a ruler of the kingdom, that was mine, while I placed myself under him as a servant of his. O king of kings, I then brought him suitable wives, having vanquished many assembled monarchs. Thou hast heard of it often. Sometime after, I was engaged in a single combat with the (great) Rama. From fear of Rama, my brother fled, the more so as his subject deserted him. During this period, he became very much attached to his wives and accordingly had an attack of phthisis. Upon his death, there was anarchy in the kingdom and the chief of the gods poured not a drop of rain (on the realm).