I play in rotation. i just started a new save, so I hadn't dealt with any old relationships yet. Yesterday for the first time, I played the Goth family which I imported from my old save. I pictured them as having a steamy relationship, as in the Adams Family.
While their romance bar was full, their attraction level was neutral. This was because they had no turn-ons and turn-offs set. Usually when I start playing a new family I do that first thing, so I had to go back into CAS and add those.
Also they were romantically unsatisfied with their relationship. This was fixed with some passionate kisses and reciting love poetry. I did install a mod by Lumpinou which prevents romantic satisfaction decay by time alone. It can still decay by game play however.