Bhīṣmadeva was not only a great family head of Mahārāja Yudhiṣṭhira, but also he was a great philosopher and friend to him, his brothers and his mother. Since Mahārāja Pāṇḍu, the father of the five brothers headed by Mahārāja Yudhiṣṭhira, had died, Bhīṣmadeva was the most affectionate grandfather of the Pāṇḍavas and caretaker of the widow daughter-in-law Kuntīdevī. Although Mahārāja Dhṛtarāṣṭra, the elder uncle of Mahārāja Yudhiṣṭhira, was there to look after them, his affection was more on the side of his hundred sons, headed by Duryodhana. Ultimately a colossal clique was fabricated to deprive the five fatherless brothers of the rightful claim of the kingdom of Hastināpura. There was great intrigue, common in imperial palaces, and the five brothers were exiled to the wilderness. But Bhīṣmadeva was always a sincerely sympathetic well-wisher, grandfather, friend and philosopher to Mahārāja Yudhiṣṭhira, even up to the last moment of his life. He died very happily by seeing Mahārāja Yudhiṣṭhira to the throne, otherwise he would have long ago quitted his material body, instead of suffering agony over the undue sufferings of the Pāṇḍavas. He was simply waiting for the opportune moment because he was sure and certain that the sons of Pāṇḍu would come out victorious in the Battlefield of Kurukṣetra, as His Lordship Śrī Kṛṣṇa was their protector. As a devotee of the Lord, he knew that the Lord's devotee cannot be vanquished at any time. Mahārāja Yudhiṣṭhira was quite aware of all these good wishes of Bhīṣmadeva, and therefore he must have been feeling the great separation. He was sorry for the separation of a great soul, and not for the material body which Bhīṣmadeva relinquished. The funeral ceremony was a necessary duty, although Bhīṣmadeva was a liberated soul. Since Bhīṣmadeva was without issue, the eldest grandson, namely Mahārāja Yudhiṣṭhira, was the rightful person to perform this ceremony. It was a great boon to Bhīṣmadeva that an equally great son of the family undertook the last rites of a great man.
Since Bhismadeva was without issue, the eldest grandson, namely Maharaja Yudhisthira, was the rightful person to perform this ceremony
SB Canto 1
Since Bhismadeva was without issue, the eldest grandson, namely Maharaja Yudhisthira, was the rightful person to perform this ceremony.
O descendant of Bhṛgu [Śaunaka], after performing funeral rituals for the dead body of Bhīṣmadeva, Mahārāja Yudhiṣṭhira was momentarily overtaken with grief.