Derick Dillard — who married into the Duggar family — has a theory as to why his in-laws are rushing to the altar in their late teens/early 20’s! The topic was brought up after a fan took to the Instagram comments section of Derick’s wife, Jill Duggar, and expressed astonishment over news that her younger brother Justin Duggar announced his engagement just a day after his 18th birthday. “Amazingly surprised that your brother is 17 and engaged!!! Why do you guys rush to marry life.