Allah, the Blessed and Exalted, says: "And if a man or a woman whose inheritance is in question is kalalah (that is, has neither parents nor children), and has a brother or a sister, then for each one of them is a sixth; but if they are more than that, they share in a third." [Surah al-Nisa: 12]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / Q12322
Sayyiduna Sa'd (may Allah be pleased with him) used to recite this verse: "And if a man or a woman whose inheritance is in question is kalalah and has a brother or a sister" [Surah al-Nisa: 12] from the mother's side.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12322
Qatadah (may Allah have mercy on him) related that Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) said in his sermon: "Indeed, this verse at the beginning of Surah al-Nisa concerning the inheritance shares, Allah revealed it about children and parents; and the second verse in Surah al-Nisa, Allah Almighty revealed it about the husband and wife and uterine brothers; and the verse at the end of Surah al-Nisa, Allah Almighty revealed it about full brothers."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12323
Kharijah bin Zayd (may Allah have mercy on him) narrates from his father (may Allah be pleased with him) that the inheritance of uterine brothers is as follows: they will not inherit alongside children, or the son's children, whether male or female, nor alongside the father or the grandfather; apart from that, one of them gets a sixth, whether male or female. If they are more than one, whether male or female, they will inherit a third and divide it equally.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12324