Japanese kinship terms

Question

How do I address someone else's great-grandchild/great-grandchildren? ひいおまごさん or ひおまごさん?

Answer 1

First off, the honorific prefix お or ご must come at the very front of a word. Neither ひい[お]{●}まごさん or ひ[お]{●}まごさん work because the ひ ("great-") and the noun it modifies cannot have anything between them. As a (very rough) analogy, it might be like saying "great mister grandchild" instead of "mister great-grandchild" -- weird enough that listeners / readers might not be able to understand the intended meaning.

(Note: This works differently for "grandparent" terms, because the お prefix has l̲e̲x̲i̲c̲a̲l̲i̲z̲e̲d̲ for those terms -- it has become part of the regular word. However, for まご, the お is still a prefix.)

Separately, I'm more accustomed to the short-"i" version ひまご, but then again my experience with Japanese has been in the Tōhoku and Kantō regions, and the long-"i" version ひいまご might be more common in other parts of Japan. That said, I do see that a couple of my dictionary resources list ひいまご as an alternative form and point the reader to look at ひまご as the main entry, so take that for what you will. :) One such example is here at Kotobank.

Lastly, Google can sometimes be helpful in getting a quick-and-dirty idea of how common different wording might be. Looking up "おひまごさん" shows me only one hit anywhere at all, while looking up "ひまごさん" shows me a little more than 1,000 hits. My guess is that the unprefixed version is used more commonly.