Musnad Ahmed: Hadith 2039

When the Messenger of Allah (ﷺ) left Makkah, ‘Ali took the daughter of Hamzah with him; 'Ali, Ja'far and Zaid disputed concerning her (i.e., who would take care of her) and referred their dispute to the Messenger of Allah (ﷺ). 'Ali said: She is the daughter of my paternal uncle and I brought her with me. Ja'far said: She is the daughter of my paternal uncle and her maternal aunt is married to me. Zaid said: She is the daughter of my brother - Zaid had become the brother of Hamzah when the Messenger of Allah (ﷺ) established bonds of brotherhood [among the believers, after the Hijrah to Madinah]. The Messenger of Allah (ﷺ) said to Zaid: “You are my mawla and her mawla." He said to 'Ali: “You are my brother and my Companion." And he said to Ja'far: "You resemble me physically and in attitude. And she should stay with her maternal aunt."