Annulments by Jimmy Akin:
First of all, illegitimacy is a (as its name suggests) is legal category, and it pertains to man’s law, not God’s. It is no stain on the child in God’s eyes if the child was born in a valid marriage, an invalid marriage, or no marriage at all. The child is equally precious to God and the Church no matter how it was conceived.
Illegitimacy is a purely human legal category that is used for such things as determining inheritance rights. As a result, if a child is born in a marriage that is valid under civil law (even if it was invalid in God’s eyes) then the child is legitimate. Thus the Code of Canon Law states:
"1137. Children conceived or born of a valid or putative marriage are legitimate."
A marriage which was invalid under God’s law but valid under man’s would count as a putative marriage.
The Code also states:
· "1138-1. The father is he whom a lawful marriage indicates unless (nisi) evident arguments prove otherwise.
· "1138-2. Children are presumed to be legitimate if they are born at least 180 days after the celebration of the marriage or within 300 days from the date when conjugal life was terminated.
· "1139. Illegitimate children are rendered legitimate through the subsequent valid or putative marriage of their parents, or through a rescript of the Holy See.
· "1140. Insofar as canonical effects are concerned, legitimized children are equivalent in everything to legitimate children unless (nisi) the law expressly states otherwise."
So the only case when a child would not be legitimate would be if it was conceived by parents who were not married even under man’s law and if they never got married. And even then legitimacy is only used for determining things like inheritance rights; it has no religious or moral significance concerning the child, who is equally precious in the eyes of God and the Church no matter how it was conceived.