As Mirrorball pointed out, this question was cleared up right at the very beginning, in the very same episode the situation was introduced. So, not to be rude or anything, but frankly you just weren't paying attention.
I grasp what the guy said. I just had a hard time wrapping my brain around the concept until another poster mentioned cellular mitosis ... then it clicked.
I also agree with the sentiment about "Dog with Two Bones." WOW.
I applaud them for their creativity though. Many people have said that Farscape is indeed a romance between John and Aeryn, a conclusion which I agree with. But in most situations like that, after the people have consummated the relationship, you end up with a generic and contrived problem to overcome before everlasting bliss and crap. But to shake things up like that