No,of course not! A (full ) nephew or niece is the child of your (full) sibling. A (full) cousins offspring would be your FIRST cousin ONCE REMOVED. The offspring of that child would be your first cousin Twice removed. This informs you exactly what the relationship is and the degree of genetic kinship.
Is my nephew's son my child's cousin?
If your cousin had a child then that child would also be your cousin example if your cousin is your first cousin then their child would be your second cousin and so on and so on.Hope that helps stressed21