Catechism of the Catholic Church §2226 — excerpt
Education in the faith by the parents should begin in the child's earliest years. This already happens when family members help one another to grow in faith by the witness of a Christian life in keeping with the Gospel.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: LG 11