Ah, so it is 
I don't remember it being in my friend's wedding but that was 8 years ago.
Technically it's a question and not a vow though 
Yes, I'm splitting hairs 
it is a part of the service.
"The most important part of a Catholic wedding is what is commonly known as the exchange of vows. These words are the heart?the essential element?of the sacrament of marriage; they form the covenant that establish the couple?s marriage. The Church calls the exchange of vows consent?that is, the act of will by which a man and a woman give themselves to each other, and accept the gift of the other. The marriage can?t happen without the declaration of consent (Catechism #1625 - 1631).
Catholic wedding vows are usually preceded by three questions from the priest:
"(Name) and (name), have you come here freely and without reservation to give yourselves to each other in marriage?"
"Will you honor each other as man and wife for the rest of your lives?"
"Will you accept children lovingly from God, and bring them up according to the law of Christ and his Church?"
The bride and groom respond "I will" or "yes" (Rite of Marriage #34).
The Rite of Marriage (#25) offers several options for Catholic wedding vows. The standard version goes like this:"
The point is many couples, even if they do get married in church, do decide not to have children and they are committing to each other, not to any possible future children, or even the op's children.