Well Sisko and Kassidy really didn't break up... they were estranged for awhile, but yeah... your girlfriend being a terrorist and getting locked up(for only a year, dang those Feds are soft!) will do that. He put up with it too. She came right back to him afterward and put up with his Bajorian Jesus stuff, so I'd say that's love.
As for Kes? Well she said Ocampa do mate for life, so I like to think that Tiernan did something she was thinking about but was a cultural taboo to her. But since it was done, she didn't want to jump right back into it with Neelix when she wasn't exactly happy with it to begin with.