I wouldn't worry about it.
Why shouldn’t I worry.
Nobody will read your book!
But the book has Excalibur and other magical things in it, so it might become a bestseller like Harry Potter.
OK, people will read your book for the same reason we read your stuff.
Unfortunately many of those people will read as much suppressed lust masquerading as moral outrage for your cousin as we do. I guess it's a result.
So maybe to prevent people from discovering that I am the same person as the author, I will eventually need to delete this account to delete all the posts I made, to delete my online presence, so that they don't discover me here and then discover my quotes on FSTDT which includes the one about my second cousin. I am more well known here than on FSTDT which has so many quotes from so many people, so it is less likely that people will discover my post about my second cousin there. But as it will take a long time to publish the book, it will be a long time before I delete this account.
By the way, does deleting an account on this site delete all the posts that the account made?