Use of real names, etc

Is this a memoir? Non- fiction?
I didn't worry about anything- just wrote my novel and my publisher had me change a name that was too close to the name of my brother in law-Even tho it was fiction- Since my MC had cognitive challenges and my brother in law had Down syndrome they felt it was too close- My point is my publisher (putnam) made the decision based on what their lawyers said.
I don't know if I would rely on any legal advice from this site tho...you get what you pay for lol!

I'd check with a lawyer who has a history of representing authors, if I were you. I read something about writers getting sued for the mere insinuation or impersonation of a real person.

You can include a disclaimer at the beginning of the book to protect yourself there, but if you're writing about a real person, I'd check with them first (for their permission, if they're still living) and then check with a lawyer too, just to be on the safe side.

No sense in having it come back to bite you in the back side later on when the person either dislikes what you wrote for some reason after it's published, or decides they want a cut of your royalties since they were your inspiration, etc. Never hurts to be on the safe side.