Jessel Howard was a distant ancestor of Dr. Beverly Crusher.

She lived in Scotland during the 1600s, and had beautiful red hair. The anaphasic lifeform Ronin took up residence with Jessel after he determined she had a biochemistry compatible with his energy signature. Ronin resided in a candle, and used Jessel in order to take corporeal form.

Many of Jessel's female descendants were hosts for Ronin for 23 generations, including Crusher, her grandmother Felisa Howard and her great-grandmother. (TNG: "Sub Rosa")

This character was only mentioned in dialogue.
Jessel was named the governess Miss Jessel in The Innocents, another story about ghostly lovers (based on Henry James' The Turn of the Screw). (Star Trek: The Next Generation Companion)