I'm not crew, but my husband is a pilot - and I have a job which involves shifts, so we both juggle our lives in interesting ways!
You'll be glad to hear that we're very happily married. It certainly is a very different type of life to married couples who both do a 9-5 - but in my opinion it has a lot of benefits, too. I truly believe that spending some time apart, although it's nasty at times, can be of benefit - you really learn to appreciate each other properly and use what time you have to the full. And life if never too predictable, which I have grown to really like. Plus, we both do jobs that we love (most of the time!) and are therefore happier as a result. We've also been able to enjoy some amazing holidays in exotic parts of the world at dirt cheap rates - which we'd never have managed otherwise!
Of course a lot of flirting etc does go on (not really surprising, given the large numbers of young single crew about!) but if you're a solid couple, you'll be absolutely fine. You just need to keep in contact regularly (we speak every day without fail) and trust each other.
Hope that helps!
Lx