sinseanathair
Great-grandfather is "Sin-seanathair".
The Irish for "great-grandfather" is "sinseanathair";I've never heard a nickname for it, although a nickname for "grandfather" is "daideo".In Irish it's "gar athair"
His great grandfather was Irish on the Kennedy side, and his grandfather on the Fitzgerald side.
If your great great great great great grandfather was from Ireland and none of your ancestors in other lines were Irish, then you would be said to be 1/128th Irish. But no one bothers with such small fractions.
sin-seanathair
If your great great great grandfather was your only ancestor from Ireland then you would be 1/32 Irish since you have 32 great great great grandparents. That would be slightly more than 3%.
She was African-American, Cherokee-Creek, and Scottish-Irish ancestry. Her great grandfather was Scottish-Irish.
In the sentence, "great-grandfather" is a compound noun. It combines two words, "great" and "grandfather," to refer specifically to a person's grandfather's father. Compound nouns can be made up of two or more words that together represent a single concept or entity.
The term is hyphenated, as great-great-grandfather(grandfather's grandfather).
She was African-American, Cherokee-Creek, and Scottish-Irish ancestry. Her great grandfather was Scottish-Irish.
Ronald Reagan was not Irish; he was of primarily English and Scottish descent. However, he did have some Irish ancestry through his paternal side, specifically from his great-great-grandfather who emigrated from Ireland. This connection has led to a cultural association with Irish heritage, which Reagan sometimes embraced.
your great great great great grandfather