Coming in quite late to note that two decade age gaps werent uncommon back in the day, nor in modern times. Fertility begins in the teenaged years and stretches into the 4th or even 5th decade. If a woman remains sexually active from her teens onward, Only infertility, birth control, or abstinence will prevent such age gaps. My paternal grandmothers first child was born in 1916 and the last, her 7th, in 1939. And people believed the baby she told them was hers in 1942 was her youngest, though actually it was her daughter's (born 1922) illegitimate child. My maternal grandmothers first child was boen in 1939' and her 6th in 1961. That youngest uncle and my older brother, born 1963, are best friends to this day. My youngest brother, my mothers 5th child, born 1980, and my oldest child, born 1984 are buddies. My 3rd and youngest child, born 2007, is a sort of big brother to his sisters child, born 2012 (she plans no more children, so i guess this habit of making full use of our fertile years is broken!)