Hello Kaija: I noticed this is your first post here on PC. So... welcome to Psych Central.

We here on PC cannot suggest mental health diagnoses. However, since your post was moved from the General Q & A forum here to the OCD forum, that presumably suggests that someone in admin thought what your family member is dealing with may be Obsessive Compulsive Disorder. And based on what you wrote, while I'm not a mental health professional, I'd say that's likely a pretty good guess. But it is important to note only a mental health professional can diagnose your family member. (We here on PC would not be in a position to say whether or not what your family member is experiencing has a hereditary component to it.)

Since it sounds as though you're here primarily for a family member one additional forum, here on PC, that may be of interest to you would be the Partners of People & Caregivers forum. Here's a link:

https://psychcentralforums.com/partn...ivers-support/

And then here are links to 8 articles, Psych Central's archives, that (hopefully) may be of help in coming to an understanding of what may be going on with your family member & how to help:

10 Things You Should Know About Delusions | Caregivers, Family & Friends

Obsessive-Compulsive Disorder (OCD) | Psych Central

11 Ways to Help a Loved One in Denial

How to Persuade Your Loved One to Seek Professional Help

https://psychcentral.com/lib/15-ways...illness/?all=1

https://blogs.psychcentral.com/careg...dium=popular17

https://psychcentral.com/blog/9-thin...ental-illness/

https://blogs.psychcentral.com/careg...dium=popular17

I hope you find PC to be of benefit.