All families have secrets. Sometimes a genealogist will learn about them and may have to face the decision of following the legal line or the biological line. That has to be up to the individual but I'm afraid DNA testing is going to blow a lot of family histories out of the water.
With memoir as the fastest growing genre in publishing a lot of questions come up about how much can and should be said. Without going in to legalities of libel and law suits it boils down to the writer/researcher's own conscience.
The phrase "write your own truth" has become the catch phrase. We can't remember every conversation, every word, every gesture that happened in a situation. We each come at an event in a different way. Consider the witnesses at a car accident. Not only will each account vary but the stories will usually change over time.
Historians and aficionados from around the world spend hours debating what happened
during the Gunfight at the O.K. Corral. The events leading up to that thirty seconds in history can't be agreed on. Witnesses saw different things, heard different things and each had their
own reason for saying what they did. Earps and Doc Holliday vs the Cowboys. The truth
will never be agreed on.
If you want to write a memoir in the hopes of publication it is important that you read memoirs. There are many books and workshops around to give you pointers in how to get started and what the publishing process is like.
Keep writing. Keep sharing and always tell your truth.