Grandfather ... Great Uncle?

What’s the skinny on usage for generational differences? I am, as of yesterday, a tearful great uncle. How come I’m not a grand uncle? The prefix -great is used for paternal and maternal lines after the first generation, as in great-great-grandmother, but not for avuncular relations.

Any ideas why?

You are both. The terms are interchangeable.

No idea why the usage. Note that it’s only the direct line that uses “grand-”, and that it goes both ways: A grandfather’s son’s son is his grandson. But your wife or sister, if any, is now a great-aunt. It may be simply that the variation highlights the distinction between direct and collateral ancestry: “great-” comes into play in the second generation for collagteral relatives, in the third for direct ancestors/descendants.

In my experience, in Ireland, “grand uncle” is used in preference to “great uncle”.

I’ve used Grand Uncle and/or Grand Aunt for years, mainly when I started doing our (E-X-T-E-N-D-E-D Family) Family Tree. It’s just something I’ve grown used to and I’m noticing many other people using it now as well.

Interesting, though, that you never hear “greatfather”, only grandfather. I suppose greatfather sounds like you’ve just been discovered by Lewis and Clark and told that some white dude back east is now your ruler.

I think in Ireland, “grand uncle” and “gran’aunt” sound more cosy or familiar, and “great uncle” and “great aunt” sound more “proper”. In other words different registers or different contexts.