When he (Maharaja Yudhisthira) could not find his uncle and aunt in the palace, naturally his doubts arose, and he conjectured that they had gone down to the water of the Ganges
SB Canto 1
Where is my well-wisher, uncle Vidura, and mother Gāndhārī, who is very afflicted due to all her sons' demise? My uncle Dhṛtarāṣṭra was also very mortified due to the death of all his sons and grandsons. Undoubtedly I am very ungrateful. Did he, therefore, take my offenses very seriously and, along with his wife, drown himself in the Ganges?
The Pāṇḍavas, especially Mahārāja Yudhiṣṭhira and Arjuna, anticipated the aftereffects of the Battle of Kurukṣetra, and therefore Arjuna declined to execute the fighting. The fight was executed by the will of the Lord, but the effects of family aggrievement, as they had thought of it before, had come to be true. Mahārāja Yudhiṣṭhira was always conscious of the great plight of his uncle Dhṛtarāṣṭra and aunt Gāndhārī, and therefore he took all possible care of them in their old age and aggrieved conditions. When, therefore, he could not find his uncle and aunt in the palace, naturally his doubts arose, and he conjectured that they had gone down to the water of the Ganges. He thought himself ungrateful because when the Pāṇḍavas were fatherless, Mahārāja Dhṛtarāṣṭra had given them all royal facilities to live, and in return he had killed all Dhṛtarāṣṭra's sons in the Battle of Kurukṣetra. As a pious man, Mahārāja Yudhiṣṭhira took into account all his unavoidable misdeeds, and he never thought of the misdeeds of his uncle and company. Dhṛtarāṣṭra had suffered the effects of his own misdeeds by the will of the Lord, but Mahārāja Yudhiṣṭhira was thinking only of his own unavoidable misdeeds. That is the nature of a good man and devotee of the Lord. A devotee never finds fault with others, but tries to find his own and thus rectify them as far as possible.