Nowadays people call it "pedophilia."
Pedophilia is when you're attracted to a child who has NOT reached puberty.
Underage is when you're under 18 or whatever age of consent. Pedophilia falls under the under-18 category…but not all underage sex counts as pedophilia. See what I'm saying?
If they were fine with being married at 16, great! As long as they could handle the responsibility.