Abu Dawood: Hadith 2266

The Prophet (ﷺ) decided regarding one who was treated as a member of a family after the death of his father, to whom he was attributed when the heirs said he was one of them, that if he was the child of a slave-woman whom the father owned when he had intercourse with her, he was included among those who sought his inclusion, but received none of the inheritance which was previously divided; he, however, received his portion of the inheritance which had not already been divided; but if the father to whom he was attributed had disowned him, he was not joined to the heirs.

If he was a child of a slave-woman whom the father did not possess or of a free woman with whom he had illicit intercourse, he was not joined to the heirs and did not inherit even if the one to whom he was attributed is the one who claimed paternity, since he was a child of fornication whether his mother was free or a slave.