We know from TNG "Sub Rosa" that the entity Ronin lived with Beverly Crusher's grandmother all her life. So how come Beverly never noticed him until after her gran's death, considering she was raised by her for quite a long while? Also, how did Ronin become linked to that ancient candle? And was he just an alien, or an alien which had visited 17th century Earth and somehow absorbed the consciousness of a human already living?
It is my understanding that Ronin did not live with Dr. Crusher's grandmother all of her life--I'm not sure it is mentioned in the episode when he became a part of her life. Based on what is said in the episode, Ronin moved from relative to relative in Dr. Crusher's family. It is possible that Felicia Howard's mother was alive when Dr. Crusher was being raised by her grandmother, and Ronin only became a part of Felicia's life after her own mother died at some unknown date after Dr. Crusher left her regular care. I never really thought the whole thing was very well explained. At the end of the episode, Dr. Crusher mentions that the candle is "plasma-based," which somehow allowed the entity that was Ronin to inhabit it. As the candle was passed down from relative to relative, so Ronin was passed down inside of it, but it isn't mentioned in the episode when the candle came into the family's possession, although it is presumed to be linked with the first Howard family member to which Ronin connected. Ronin never mentioned where he came from, so it is hard to classify him. He says that he lived with Dr. Crusher's distant relative in the mid-17th century and this set of the chain of events that brought him to the "present time" reflected in the episode.
The episode is so silly, that dwelling on it too much is kind of self defeating. There was no logic to the episode at all.
I taped this when it first aired. The only impressive thing I found about the episode was how director Jonathan Frakes and his director of cinematography made Gates McFadden look more beautiful than she ever had before.
That and her "self gratification" scene. But, yeah, I'd rather forget this episode existed. The story should have stayed in the supermarket romance novel with Fabio on the cover it came from.