Do you have a cousin? Does that cousin have any children? They are your first-cousins once removed.
By the same token: The cousins of your parents are your first-cousins once-removed.
Regards,
Thanks. Here they are referred to as second cousins. I’ve never heard “once removed” before. Maybe it is a colloquial thing.
My first cousin’s children are my second cousins. My parents’ first cousins are my second cousins.