The statement in my memoir is one made to a therapist concerning a traumatic event perpetrated on my sister. It plays a part in why I became depressed and anorexic, which is why I'm considering mentioning it in the story. The perpetrator was a family member who, believe it or not, I still care for deeply, so there is no malice intended.
I'm writing this for my children, first and foremost. I may consider publication, but would likely edit some things out if possible, first.
Ah, yes, writing to expose the skeletons can definitely defuse their power over you, and answer questions for those who grow up in the shadow of an unseen beast.
Three generations up my family tree looms an ancestor who is rumored to have had a fondness for young girls. It's a complicated story. Rumors abound within my bevy of cousins, along with speculation about what really happened, and whether that was what made X the way she was and contributed to Y's aberrations. In the long run, it doesn't matter. We are all where we are, for better or worse. But, in the long run, knowing for sure might awaken a bit more compassion for X, who was a wicket witch as far as many of her descendants are concerned.
I've asked the few who are left in an earlier generation with more direct knowledge. They utter platitudes like, "Well, things were different back then," that neither deny nor confirm it. I'm in the process of weaving together an inferred family history that takes this influence into account (clearly labeling the inferences).
A couple of people in a lifestory writing group I lead have had the devil of a time writing about some similar incidents in their own family backgrounds. They are simply stuck, unable to write about it, and unable to forget.
So, bravo for you, Pat, quieting these rattling bones for your children. The matter won't die. It's going to persist in whispered rumors across layers of cousins and into the future. I think they'll be glad to know, and I'll bet a dime to a dollar that the information leaks out into the larger cousinhood and family. If you haven't written to villanize, you can certainly hope for the best. Oh, for easy answers!
In my case, the people I'm writing about have been cold in the ground for anywhere from a century to a decade, so there's nobody left to directly offend.
One thought: If your only reference to the matter is the one sentence to your therapist, you may awaken more curiosity than you satisfy. You may need to flesh it out a bit, and weave it in a couple of other places to anchor it and fully put it in perspective -- especially considering that your perspective seems somehow to have enabled you to make peace with your own feelings about the perp.