If the competent heirs acknowledge a person of unknown lineage, and that person confirms their statement—or if he is a minor or mentally incapacitated—both his kinship to the deceased and his share of the estate are thereby established.

However, for his kinship to the deceased to stand, every heir—including the spouse and the uterine sibling—must concur in the acknowledgment, or else two upright witnesses, whether heirs or outsiders, must testify to it.

If all the heirs do not acknowledge1 him, his lineage and right of succession are valid only vis-à-vis the heir who did; he will therefore share whatever part of the estate that heir still holds, or take all of it if the latter has already relinquished his share.