Mormons also tend to have more children than other groups. Mormons ages 40-59 have had an average of 3.4 children in their lifetime, well above the comparable figure for all Americans in that age range (2.1) and higher than any other religious group. Overall, Mormon adults have an average of 1.1 children currently living at home, nearly double the national average (0.6).

http://www.pewresearch.org/fact-tank/2015/05/22/mormons-more-likely-to-marry-have-more-children-than-other-u-s-religious-groups/