Being third cousins mean we share a great-great grandfather. Being second cousins once removed mean that we share the same great-great grandfather, only they would call him a great grandfather. So, “once removed” describes a generational layer difference.
Layer may not be a genealogical term, but you get the idea.
In Fiji, if you’re a respected older person, you’re called uncle. I call both my actual aunt aunty, and my second cousins once removed aunty. My third cousins once removed (which are the children of my third cousins) call me uncle. Or at least that’s what their moms tried to get them to call me; the best we could do was get them to wave at me.
I also refer to close family friends of my aunty and father as aunty and uncle. Their children are my cousins. Sitting next to me in the above photo is my Uncle Cegu — no blood relation, but he’s very close to our family (and a wonderfully nice guy).
My children have fourth cousins, which are the closest relatives they have (of their generational layer) on my dad’s side.
On my wife’s side of the family, she being someone who has siblings, they have first cousins. They also have second cousins through my mom’s side of the family, if you were wondering.
What’s nice about Fiji is I was received like the long-lost son who finally returned to the motherland (or literally, the father’s land in this case). Anyway, everyone there made me feel overwhelmingly welcome. And after a few weeks of being back, I still miss them all very much.