From the IMDb Help Center:
Claim Your Page - It says my IMDb page is claimed, what can I do?
If you are certain you didn't create the membership claiming your page and you're unable to determine who did, please visit the Contact Us page while logged into your IMDbPro account.IMDb Contact Us Page Link
Click the following buttons/drop-down items on the Contact Us form.
IMDbPro member questions > Other data types > Other data issue > Email
In the Enter additional information box, write a statement that you would like to claim your father's IMDb name page. Include the URL of the name page and any other information you believe is relevant.
You should receive an email response from an IMDb representative within 24 hours.
I hope this helps.
I would like to know who controls my fathers IMDB site?The answer to this question is: nobody. Just like all IMDb name pages, nobody has exclusive control over the content.
A good place to start is -> https://help.imdb.com/article/contribution/contribution-information/how-do-i-contribute-data-to-imdb/GVZTHQ48SWS47WDK
"Pages on IMDb feature an "Edit Page" button near the bottom. To add information or to correct existing information, you just need to click the button and follow the instructions on the following pages."
Claiming a name page as an active IMDbPro subscriber gives additional benefits outside of the core IMDb data for the page, but this does not appear to be the spirit of the question being asked above. Please also see https://help.imdb.com/article/imdbpro/manage-your-imdb-page/claim-your-page/GXWAJBBV8EVPF3PE
David, does this help?
As Col mentioned your fathers page is controlled by no one person. However, if there are certain inaccuracies in his mini-bio that you wish to address and edit. Here is an explanation on how this is done. You can also add additional data too.
How can I update a biography?
A name page can only list a single biography, however we welcome updates and corrections to keep these current - to update an existing biography, please see the following instructions:
1. Go to that person's page.
2. Click on the "Edit page" button towards the bottom.
3. Next to the "Biography" option click the drop down and select "Correct/Delete".
4. Scroll to the bottom of the page and select "Continue".
5. Next to the biography, click the drop down and select "Correct" and then "Check these updates" at the bottom of the page.
6. Input the new corrections into the field, making sure it's in line with our Mini-Biography guidelines.
7. Click "Check these updates" and correct any errors you're presented with.
8. Press "Submit".
You can also edit inaccuracies in his personal trivia also. At the bottom of this picture is where you can edit those items. You can also add new trivia items too.
And a Happy Early Birthday to you.
I turned 64 myself this year!