Did the man and woman take the following vow?
I, N.N., take thee N.N., for my lawful wife (husband), to have and to hold, from this day forward, for better, for worse, for richer, for poorer, in sickness and in health, until death do us part.
It would seem to me that a married couple in the situation described should carry the cross they must bear and help each in their quest for salvation.
Everyone thought St. Elizabeth, the cousin of the Blessed Virgin was infertile, but it turned out their prayers and sacrifices were heard by God.