Is the lineage of an additional heir established if all heirs acknowledge him?

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The lineage of an heir is established if all heirs acknowledge him, or if the deceased acknowledged him during his life to prove that lineage. This position is held by Al-Nakha'i and Al-Shafi'i. The evidence is the precedent where 'Abdullah ibn Zam'ah claimed the lineage of his father's concubine's child, stating, 'This is my brother, born on my father's bed,' and the Prophet, peace be upon him, accepted his statement and established the lineage based on it. Furthermore, the heir stands in the place of the deceased, evidenced by the fact that an heir's admission establishes debts or other matters that the deceased's admission would establish against himself, and lineage falls under this category as the heir succeeds the deceased in his rights, including this one.