A marriage to a non-baptized person can be especially difficult because of the greater chasm in religious belief.In either case the disparities between faiths can lead to tension and gradually religious indifference.Children are often considered fruit of a marriage, but the ability to bear children is not a prerequisite to marriage.
It is a union that God has brought together and no person is able to dissolve that union.
The annulment process is not a Catholic divorce, but rather it is a process that determines if the marriage was ever really a marriage (meeting the conditions above for a sacramental marriage).
The Catholic person must uphold the obligation to preserve his or her own faith and “ensure the baptism and education of the children in the Catholic Church,” (Catechism of the Catholic Church, 1635).
One of the reasons that the Church exists is to safeguard the souls of those in its care.
If a Catholic insists on marriage to a non-Catholic, the Church allows it, but wants to protect the soul of the Catholic in the marriage by making sure the non-Catholic understands the moral teaching and obligations of the Catholic party and assure that the Catholic is not in a position hostile to his or her faith.