There is a wide spectrum of thought about children, among Catholics. Some love lots and lots of children, and others prefer just a few, or even none at all. I think that Catholicism can accommodate all of those preferences.
At this point, I wish to distance myself from the childfree extremists. Some of them hate and disrespect both children and parents. I strongly disagree with their viewpoint.
I am just a single man, who never wanted to have any kids, nor to have a woman who had kids. I do not dislike children any more than I dislike elephants. But I do not want either kids or elephants in my home.
Clearly, I am unorthodox about marriage and children, and that is something that I have to live with.
MagickMan… I too am childfree. And I do not mean it disrespectfully (and it was NOT created out of disrespect towards children and families. That is a misconception.) I do not use the word “childless” since it implies I wanted them but just don’t have them.
There will be people who will always ask you to “consider your motives” - and many erroneously believe it is for selfish reasons that you do not want children. What I have learned is that people who have always wanted children, or people who have “maybe” wanted children, many times do not understand that there are people who, simply put, do not want children. Then you have some who said they didn’t want children and when they had them say many different things like, “I thought I didn’t want them” or some other such sentiment. That’s fine, that’s them. No one can know another person’s mind and heart.
I have not wanted children since I was a child. I grew up with comments like, “You don’t know what you’re talking about,” “You just need to grow up,” “You just need to find a good Catholic man,” and “You’ll change your mind.” They are wrong.
At 40 years old I have not changed my mind. Nor do I intend to. In fact, I have done far more introspection on children and whether I wanted them than some other people have. I have come to the same conclusion since I was a kid: I don’t want them. Period. I used to come up with excuses, but that is because people can’t handle a simple “No” and insist there must be SOME REASON because, surely, it’s UNNATURAL that a person does not want children!
Generally speaking, people who have children or want them cannot fathom that there are some people who have no desire to have them. Some can understand, though most parents cannot. It’s worse for women since we have “the plumbing.” Surely, since we can create life, we must want children!
Uh. No.
Then men get the “you must carry on the family name” or “you need to grow up” or “he’ll change his mind when he sees his own child” lines. It’s tough all around.
At any rate, I want to say to not let anyone tell you you are being selfish. I have seen far more parents be selfish once they have children than those who have no children. (I can give some anecdotal “evidence” in my own life, but I won’t go into details here.)
Okay, all of that being said, here is a Catholic answer. (The above is my “secular” answer.

) All of this is said under the context of being Catholic - as this is a Catholic forum.
Marriage is a vocation. As with vocations, there may or may not be a calling to said vocation. Part of marriage is to be open to any possible life that God may bring into the marriage. i.e. You may, or may not, have children. Some people just end up infertile and it does not mean that their marriage is any less valid, as has been explained in other posts.
As human beings, of course we want companionship. We’re social creatures. We’ll probably find someone and fall in love and want to commit to them for the rest of our lives as we have found The One. This is natural. For some people, and I know a few, what is “natural” for them is to stay single. They are able to be of service for other people without the commitments marriage and parenthood brings. There is nothing wrong with that.
Now. What I am about to say is going to be tough. I had someone tell this to me and it angered me. However, over time, I have been able to accept this, considering that marriage is a vocation, and not just some “bff” thing. Your lack of a desire for children may very well be an indicator that you are not being called to the vocation of marriage, as understood in the Catholic church.
I’ll be honest here. I don’t want children. At all. Period. I don’t carry babies, nor do I babysit. However, were I to get married, and it would be a Catholic marriage, I would have to willing to accept the possibility that I may get pregnant. (A thought that, really, I just loathe.)
btw, I have met a Catholic man I do wish to marry. We have no plans on that, however. And he too does not want children at all. So. We don’t marry.