It is narrated from al-Sha'bi (may Allah have mercy on him) that the first to inherit as a grandfather in Islam was Sayyiduna Umar (may Allah be pleased with him). A certain grandson of his died, and Sayyiduna Umar (may Allah be pleased with him) intended to take his wealth to the exclusion of his brothers. Sayyiduna Ali and Zayd (may Allah be pleased with them both) said to him: That is not your right. Sayyiduna Umar (may Allah be pleased with him) said: Had the two of you not agreed in your opinion, I would not have thought that he was my son, nor that I was his father.
This is mursal; al-Sha'bi did not live in the days of Umar, but it is a good mursal.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12427