Can a marriage that was initially invalid (but not because of an impediment) become valid later on? In particular, if a couple had entered marriage intending never to have children, but subsequently changed their minds and had a child, behaving in all respects as a normal married couple, would the marriage remain invalid? And if so, what would need to be done to make it valid?
The intention of never having children does indeed invalidate what would have been a valid marriage, all things being considered. If the couple should change their intention and decide to be open to having children, then the marriage becomes valid. I just dealt with a couple who did this.
Fr. Vincent Serpa, O.P.