Your First Cousin's child is your first cousin, once removed.
The child of your father's first cousin is your second cousin
Your first cousin's children are your first cousins, once removed. Your second cousin's children are your second cousins, once removed.
The children of your first cousin are your first cousins, once removed.
Your niece and your child are first cousins. Your niece's child and your child are first cousins, once removed. The children of your niece's child and of your child are second cousins to each other.
Your cousins child is your first cousin once removed.
Because that is the way it works. Your cousin's child is your cousin once removed because you are separated by one generation while you and your cousin are of the same generation. Your cousin's child is not your neice or nephew because that relationship is reserved for the children of your brothers and sisters.
Your child and your first cousin's child are second cousins. Your child and your second cousin's child are third cousins to each other.
AnswerSince they would also be cousins, call them by their first name. AnswerYour children and your first cousin are first cousins, once removed. Your children and your second cousin are second cousins, once removed.
Your child and your niece are first cousins to each other. Your child and your niece's child are first cousins, once removed.
Your child and your nephew are first cousins. Your child and your great nephew are first cousins, once removed.
Your child and your first cousin's child are second cousins. A full generation is another set of cousins. For example, the second cousins' children will be third cousins, etc. Now here is the tricky part. You are a first cousin once removed to your cousin's child and your cousin is a first cousin once removed from your child.