Obviously, we cannot know what people do in their bedrooms, but there are plenty of ‘devout’ Catholics that don’t use artificial birth control and have enough love in their family to accept all children as gifts from God and not abort them.
Now, my answer to the original post. I would assume that if the couple was Catholic ‘enough’ to want a large family and not use artificial forms of birth control, I also assume that couple would want to breastfeed their children if at all possible. Breastfeeding does space babies. Lets say your fertility returns after a year of nursing as exclusively as possible. Then your babies would be 21-24 months apart, probably. Then, lets assume the woman has this ‘normal’ fertility until she’s 40. [You can talk to many doctors and they will generally tell you that fertility changes throughout a woman’s life (duh) and the decrease starts around 32, then another change at 35, 40, and 45. The only thing ‘normal’ is that no woman is ‘normal.’] That being said, a 23 year old might have 17 years or about 204 months of fertility. If the babies are spaced 21-24 months apart because of breastfeeding, I would say about 8-10 children.
This family is very generous and will be given all the grace needed to raise this family. However, if at anytime the couple wants to space the children further or decides that another child would be irresponsible because of financial, emotional, etc problems, the CCC requires us to do the responsible thing and use periodic abstinence, ie NFP, to avoid pregnancy. The Church is very clear that it does not want families to have as many children as they possibly can during their fertile years, but instead want families to welcome new additions as gifts from God and wants couples to prayerfully discern how many children is right for their family. Whether 1 or 15, a couple needs to discern if they should be avoid pregnancy every month. Re-evaluation definitely needs to be done very often based on the needs of the family at the time. One thing is certain, though, you cannot predict everything that will happen in your life and you cannot expect to definitely know when you get married how many children God will want you to welcome into your lives.
God Bless,
laomath