You could be second cousins. Or you could be no relationship at all if they do not share a common ancestor with you.
I believe they would be great aunts or great uncles.
great nephew
In English language terms for family relationships, there is no relationship called "nephew once removed." The son of your nephew is your great nephew.
You're a Great Aunt to your nephew's son, who is your great nephew.
You are your nephew's uncle, or aunt, and his son's great uncle, or great aunt. Your nephew's son is your great nephew.
Your nephew's grand son is your great great nephew and you are his great great uncle (or aunt)
You are your great nephew's great uncle or great aunt, depending on your sex.
First cousins, twice removed. Aunts daughter is your cousin. Aunts daughters daughter is cousin once removed Aunts daughters daughters daughter is cousin twice removed.
Your grandfather's great nephew is your second cousin.
The English language has no relationship name for the wife of your great niece or great nephew.
In English cousin denotes a family relationship, it is not gender specific.
Your great grandfather's sister is your great great aunt. You are her great great niece or great great nephew, depending on your sex.