The right to identity documents is one of the basic rights of individuals from birth and cannot be related to the legitimacy or illegitimacy of the relationship between their parents. Children born from illegitimate relationships in Iran are born as a result of adultery and according to the laws, these children are attached to the adulterer and the adulteress, and the rights and duties that the law and custom provide for legitimate children are also applicable to illegitimate children. The issue discussed in this research is the gross difference between legitimate and illegitimate children in terms of their identity documents, which will be visible and tangible if the adulterer, or in other words, the father of the child, does not obtain an identity card. In this article, the issuance of identity documents for illegitimate children has been comparatively examined in custom, law, and international documents, and appropriate and efficient legal solutions have been proposed to reduce this difference between children and, consequently, humans.