When you dance, you spend a ton of time at the studio, in rehearsals, on stage, traveling on tour... it doesn't leave you a ton of time to socialize with non-dancers. Plus, it's such a rarefied world, who could ever understand what your life is like on a daily basis? Thus, it's no surprise that dancers end up dating and marrying other dancers.
Here's a quick-list of married/engaged dancers:
Ethan Stiefel and Gillian Murphy (American Ballet Theatre)
Jose Manuel Carreno and Melanie Hamrick (ABT)
Sascha Radetsky and Stella Abrera (ABT)
Sarah Lane and Luis Ribagorda (ABT)
Megan Fairchild and Andrew Veyette (NYCB)
Robert Fairchild and Tiler Peck (NYCB)
Janie Taylor and Sebastien Marcovici (NYCB)
Vanessa Zahorian and David Karapetyan (San Francisco Ballet)
Aurelie Dupont and Jeremie Belingard (Paris Opera Ballet)
Ekaterina Kondaurova and Islom Baimurodov (Mariinsky Ballet)
Natalia Osipova and Ivan Vasiliev (ENB)
Alina Cojocaru and Johan Kobborg (formerly Royal Ballet)
Herman Cornejo and Carmen Corella (ABT, Boston Ballet)
Erica Cornejo and Carlos Molina (Boston Ballet)
Denis and Anastasia Matvienko (Mariinsky Ballet)
Again, I'm sure there are tons more... just a sampling!