3 is normal. 5 is as large as I’ve seen.
Nonetheless, where there’s a will there’s a way. A 30 year old male would probably marry a somewhat younger female, so let’s say she gives birth every 2.75 years. That’s about 40 on her 5th child, so that’s really not that hard.
We have a couple (Catholic) up the road with 13 kids. She’s actually very young for 13 kids, and (apparently) very fertile.
Her oldest is only about 25....my wife taught him in her math class. Where there’s a will.......
I dated a Catholic girl back in High School with 13 kids in their family. She and a sister were born in the same year. Then a brother born the following year, and two more brothers born in the same year following that IIRC. Real neat family, and an interesting study in demographics with all of the issues and problems that a sample of 13 people might give.