I was reminded of this by the "What do your DC call their grandparents" thread... what do your DC call their cousins' grandparents (if anything - obviously lots won't know them)?
I guess in a lot of cases they'll only ever meet at birthday parties, or be talked about, but I'm curious as to what other people do. When I was younger, we called our cousins' GPs Granny/Granda Surname, same as our own GPs, but we knew they weren't our actual GPs. DH thinks this is odd and confusing and they should just call them by their first names, but I think that's a bit forward.
What do others do?