She gave him a lung and dared him to have a baby with her. He tried to kill Tom Paris for looking at her funny, and yelled at her for knowing where other men lived...
Sounds like a regular relationship to me.
Wow, if I'm in a relationship like that, god help me.

Seriously though, the lung thing I can understand but it was so early into the series when we believed there was a relationship. When was the whole baby thing? I don't recall that episode?