The Souhrada Family Website
This explanation of cousin relationships is courtesy of Carolyn H. Jett.
Many people don't understand the difference between "second cousin" and "first cousin once removed." (Hopefully, the following diagram and illustration will help!)
In this example, Albert is the father of Bill and Charles (brothers). Bill's son is Daniel, and Charles' son is Everett. Daniel and Everett are first cousins. (No problem yet, right?)
Daniel's son is Frank and Everett's son is George. Frank and George are second cousins.
Daniel and George are first cousins once removed. Everett and Frank are first cousins once removed. (That is, first cousins Daniel & Everett are the closest relationship, and they are one generation removed from that relationship.)
Moving on, Frank's son is Harry, and George's son is Ingram. Harry and Ingram are third cousins. Frank and Ingram are second cousins once removed, and George and Harry are second cousins once removed.
Daniel and Ingram are first cousins twice removed, and Everett and Harry also are first cousins twice removed.
Now you understand cousin relationships!