My daughter just got engaged. She is 19, he is 17. They've been together for 4 years, but friends for much longer. He proposed with his mother's blessing and a family heirloom ring. He's known, since he's twelve, that he wanted to marry my daughter. They've already battled and come through a lot, including illness, long distance, family/friends trying to draw them apart, and many more things that have torn more "mature" couples apart. They are planning for a Halloween 2015 wedding, after they've both graduated all their schooling. They have a budget and are saving for it, with enough to have a decent next egg, too. Some people who have seen them go through all this still are telling them they're too young to think about getting married. How can I tell these naysaying friends and family members that these "kids" have their heads screwed on better about this than most of those doing the "well, don't worry, things could change by then" when I am so proud and happy for my daughter and FSIL?