@kirkfan: From what little we hear in the episode, neither parent actually carries the young. That's what the 'fibrous husks' are for. The parents inseminate that husk (and I would think that to do so, they'd have to have some kind of sex organs), but they don't actually carry the babies.
We don't know, specifically, whether the J'naii actually have romantic relationships and/or can have sex purely for recreation, although there's no real evidence (for either) that they can't.
We don't know, specifically, whether the J'naii actually have romantic relationships and/or can have sex purely for recreation, although there's no real evidence (for either) that they can't.