It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that Hamzah (may Allah be pleased with him), the paternal uncle of the Messenger of Allah (peace and blessings be upon him), was the brother of Zayd bin Harithah (may Allah be pleased with him); the Messenger of Allah (peace and blessings be upon him) had established brotherhood between the two of them.
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4644