Behold, the Disney princesses' ages:

And here's something unsettling.

Short answer: way too young to be getting married.
From left to right: Jasmine from Aladdin (15), Pocahontas (18), Cinderella (19), Mulan (16), Tiana from The Princess and the Frog (19), Ariel from The Little Mermaid (16), Rapunzel from Tangled (18), Belle from Beauty and the Beast (17), Aurora from Sleeping Beauty (16), Snow White (14).
All ages found here.
None of the Disney princes have official ages. The only prince we can really assign an age to is John Smith, who was 27 when he encountered Pocahontas' tribe. Of course, the real Pocahontas wasn't 18 in 1607 — she was 12.