what is a 2nd cousin

A second cousin is a relative who shares a great-grandparent with you. To calculate cousin relationships, it is important to know that cousins share a common ancestor that is at least 2 generations away, such as a grandparent or great-grandparent. Second cousins are the children of your parents first cousins. You and your second cousins have the same great-grandparents and typically share 3.125 percent of your second cousin’s DNA. It is also important to note that a second cousin once removed is either the child of your second cousin or the parent of your third cousin. They are "once removed" because you are separated by 1 or more generations.