Well, if you married Catholic you are supposed to have taken the sacrament of marriage. Taking the sacrament of marriage introduces the couple into an ecclesial order, meaning you are making a commitment not only to your spouse but also to the Church and to God. You have to make three promises:
- that the marriage will be permanent
- that you will remain faithful to your spouse
- that you will be open to having children
The theological reason children is included is because procreation and education of children is the ultimate purpose of marriage:
“By their very nature, the institution of matrimony itself and conjugal love are ordained for the procreation and education of children, and find in them their ultimate crown.”
~Pope Paul VI, Gaudium et spes 48
~as quoted by the Catechism of the Catholic Church, The Sacrament of Matrimony: The Goods and Requirements of Conjugal Love, Chapter 3, Article 7, section V at 1652
IIRC the importance of child-bearing and marriage in Catholic teachings was originally a counter to some (medieval?) Gnostic sect that taught the God of the Old Testament who created the physical world was Satan, and to ascend to heaven one had to renounce all material pleasures, including sex, children, and before the last rites, the thing that I remember this because of, they would renounce food.
If you didn’t marry Catholic, and didn’t take the sacrament of marriage, the Pope isn’t talking about or otherwise criticizing you.
~Max