At the SSPX chapel, there are two families of 10 chldren and one family of 8 children, another of 6 children and lots with 5.
Funny, at the novus ordo church, 3 seems to be the largest with 2 being norm. Of course, this makes sense since the "god" of the novus ordites is "this world".
Just remember, though, that not every family gets to have 10 children. Especially nowadays, when it's so hard to find that "special someone" to commit to for life. Marriage is serious business, and it can take a while for a man to get established AND find a suitable spouse.
If you get married in your late 20's, you're less likely to have 12 children.
There is a thing called a "miscarriage", plus some women choose to feed their babies the food God designed for them ("breastfeeding"), which usually delays the return of fertility as a side effect.
We need to catch ourselves when we judge how "Trad" someone is by how many children they have. What if they're perfectly Trad but only have 6 children? Do you accuse them (even to their face) of using birth control? I've heard of such things happening, which is disgusting to say the least.
Yes, generally speaking families are not going to have 2-3 children if they're not "preventing". But even if you come across a Trad family with 2 children, PLEASE don't judge them if you don't even know them. It's not Christian, let alone Catholic.