“I heard the Prophet ﷺ when a case was brought to him which involved the share of a grandfather. He gave him one third, or one sixth.” (Using translation from Ibn Mājah 2722)
سَمِعْتُ النَّبِيَّ ﷺ «أُتِيَ بِفَرِيضَةٍ فِيهَا جَدٌّ فَأَعْطَاهُ ثُلُثَا أَوْ سُدُسًا»