Is it permissible for a child born from an illegitimate relationship (Zina) to be attributed to a mother who is not his biological mother?

If the husband fathers his child through a lawful means (from a valid marriage followed by divorce), then the child is legally attributed to him. It is not permissible for the husband to claim that the child is yours, as this is a lie and forbidden (haram), and it leads to corrupting consequences such as the child being ignorant of his true mother, the severing of kinship ties, the loss of rights such as inheritance, and your sisters treating him as a mahram when he is not.

However, if the husband fathers his child through unlawful means (such as adultery), then the child is attributed only to the mother who gave birth to him, and it is not permissible to attribute him to you or to your husband.