Claim Titles Under a separate IMDb list?

Robert: Assuming that all the information on the Robert Marshall (IX) (https://www.imdb.com/name/nm2051351/) and Robert Marshall (XL) (https://www.imdb.com/name/nm10386108/) pages refers to you, you should merge the two name pages.

To do this, go to the Robert Marshall (XL) page at https://www.imdb.com/name/nm10386108/. Click "Edit page".

On the next screen, on the Name Correction or Merge line, select "Add correction". Scroll down and click "Continue".

On the next screen, below the box that begins "This form has 2 purposes ...", there will be a blank line on which to enter the corrected name. Enter it as:

Marshall, Robert (IX)

Un-check the box marked "Preserve previous name on existing credits. i.e. '(as Robert Marshall)'" -- it doesn't apply to this situation.

In the Explanation box, enter something like this:

I am Robert Marshall (IX), and my credits have been split between two roman numerals. All the credits on both the Robert Marshall (IX) and Robert Marshall (XL) pages belong to me, and so these two name pages should be merged.

Click "Check these updates".

On the next screen, you will get a warning that begins, "You are about to merge two separate name pages into one ...." That's what you want, so check the box marked "Warning understood, go ahead anyway." Click "Re-check these updates".

On the next screen, your data should appear with a green background, and you should be able to click "Submit these updates".

Allow a few days for the correction to go through. Good luck!