Marriage is a Holy Mystery and a school of sanctity, and children are part of that school of sanctity. It is not surprising that saints often have children who are saints as our homes are to be domestic churches where our children can grow in holiness.
As we lead our children to God, our precious children can help lead us to God in many ways. They teach us to love others, to be grateful, to be less selfish, and to be more careful. They are truly a gift from the Lord. For example, if we have the habit of cussing, our children will exaggerate and use those cuss words at every convenient opportunity embarrassing us and helping us to stop and watch our speech. In fact, our priest gave a sermon about this. Once a man came to confession, as he was concerned about the words coming out of his children's mouth. When the priest mentioned that he had heard him say those very words, the man was red-faced, and shortly cleaned up his speech. In addition, he started praying and leading the prayers at home. In fact, he became a model of Christian kindness. This is why the Church says that Marriage is a school of sanctity.