Musannaf Ibn Abi Shayba 26:351

Waki’ narrated to us, he said: Al-Hakam ibn ‘Atiyyah narrated to us, he said: I asked Al-Hasan about the *hamil* (a person of unknown lineage) who establishes evidence that he is his brother. He said: He inherits from him according to the Book of Allah: "But those of [blood] relationship are more entitled to inheritance in the decree of Allah."