Your first cousin's child is your first cousin once removed.
Your cousins child is your first cousin once removed.
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.
The relationship between your sister's (or brother's) child and your cousin is the same as the relationship between your child and your cousin. Your child and your first cousin are first cousins, once removed. Your child and your second cousin are second cousins, once removed, and so forth.
Your son and your 1st cousin's child are 2nd cousins.
Your first-cousin and your child are first cousins, once removed.
You are second cousins
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 first cousin's child's child (your first cousin's grandchild) is yopur first cousin twice removed.
The child of your father's first cousin would be your first cousin, once removed. Then when that person has a child, their child will be your first cousin, three times removed. A second cousin is the children of first cousins. For example, your child and your cousin's child are second cousins. Then their children will be second cousins, once removed to each other.
The child of your first cousin is your first cousin, once removed.Your child and the child of your first cousin are second cousins to each other.
Your second cousin's child is your second cousin, once removed. Your second cousin's child and your child are third cousins to each other.
Your first cousin's child is your child's second cousin. Your second cousin's child is your child's third cousin. Your third cousin's child is your child's fourth cousin. and so forth