Musannaf Ibn Abi Shayba 34:189

Abu Usama narrated to us, from Mujalid, who said: 'Amir informed us that the first grandfather to dispute with his sons' sons was Umar ibn al-Khattab. His son died and left two sons, so he disputed with them before Zayd ibn Thabit. Umar saw him looking into their affair, so he said, "Who is disputing with me regarding my children?" Zayd said, "They have a father other than you," so he made them partners.