Arthur
Arthur Spiderwick.
Your grandmother's nephew would be your parent's first cousin. They would be your first cousin once removed. Since the child of your cousin is a generation away from you they are the once removed.
You are first cousin, once removed to the children of your great uncle.
Your sister's son is your nephew. Your uncle is your nephew's grand uncle or great uncle.
Your great uncle's granddaughter is your second cousin.
Your great uncle's grandchild is your second cousin. (Your great uncle's child is your first cousin, once removed and your parent's first cousin.)
Your great great great uncle is the brother of one of your great great grandparents. Your great great great uncle's son is the first cousin of you great grandparents, so he is your first cousin, three times removed.
The uncle's nephew would be first cousins with the uncle's children. So the nephew would be a first cousin twice removed with the great granddaughter.
If your uncle is someone else's great uncle, you and that other person are first cousins, once removed.
You and your uncle's great grandchild are first cousin, twice removed.
Your great uncle's child would be your second cousin. I think technically it is your first cousin, once removed! Second cousins, are cousins of cousins.
The child of your great uncle is the first cousin to your mother or your father, and is your first cousin, once removed.
Your great uncle's children are your parent's first cousins and your first cousins once removed.