Fourth cousin once removed.
Your first cousin's daughter and your son are second cousins to each other. Your second cousin's daughter and your son are third cousins to each other. Your third cousin's daughter and your son are fourth cousins to each other. And so forth.
Your first cousin's daughter and your son are second cousins to each other. Your second cousin's daughter and your son are third cousins to each other. Your third cousin's daughter and your son are fourth cousins to each other. And so forth.
Your first cousin's daughter is your first cousin, once removed.
Your cousin's daughter is your first cousin once removed. Your daughter and your cousin's daughter would be second cousins.
Your cousin's daughter is called your first cousin, once removed. Although the term "second cousin" is sometimes used for this relationship, it is technically incorrect.
Your aunt's daughter is your first cousin and herdaughter is your first cousin once removed.
If it is your first cousin, they are your first cousin once removed.
The offspring of your first cousin is your first cousin once removed.
The son, or daughter, of your father's first cousin is your 2nd cousin. The son, or daughter, of your father's second cousins is your third cousin. The son, or daughter, of your father's third cousin is your fourth cousin. And so on.
Your daughter and your second cousin are second cousins, once removed.
Your son and the daughter of your first cousin are second cousins to each other. The daughter of your first cousin is your first cousin once removed.
2nd cousin.