AFAIK, The O'Callaghan speaks English well enough. He may not be interested, which is OK.

I'm also aware of the McCarthy problem that led to the IRO ceasing to record Irish titles of nobility.

The relevant part of the Irish constitution states:

1° Titles of nobility shall not be conferred by the State.

2° No title of nobility or of honour may be accepted by any citizen except with the prior approval of the Government.

The IRO used to keep track of old existing Irish titles of nobility and their descent, before they stopped doing so, and I assume that they considered that existing hereditary titles are automatic and are neither "conferred by the State" nor "accepted by any citizen", but that they just exist as a fact on the ground. I know the IRO justified tracking them on the basis that titles are property, but that didn't stop them from ceasing to do it.

As far as such titles relate to defining who is the chief of a clan, then I suppose this relates to clans, but there is nothing here about clans, let alone whether any official can determine whether they are in existence or not.

Scotland is of course, another matter, but I personally would defer to Jock.