A The key to figuring out how two relatives are related is to trace back to the most recent ancestor they share. For example:
* first cousins share grandparents
* second cousins share great-grandparents
* third cousins share great-great-grandparents
… and so on. But it gets confusing when you start mixing generations—that’s where “removeds” come in. Draw a picture if you have to. For example, say Mark is my sister Sue’s son and John is my cousin. This shows Edna is their most recent common ancestor:
Then, figure out how each person is related to the common ancestor. Edna is John’s grandmother and Mark’s great-grandmother.
Then you’re ready to use a relationship chart (click to download ours, which goes up to sixth-great-grandparents, as a PDF) or an online tool to figure out the relationship.
To use a chart, look at the top row and pick out one descendant’s relationship to the common ancestor (Mark’s is highlighted in blue in the example below). In the left column, find the relationship for the other descendant (John’s is red). Look where the row and column meet: The lavender square shows the boys are first cousins, once removed:
Fortunately, you also can use an online “cousin calculator” such as this one to do the same thing. Just select the relationship of each person to the common ancestor, and you’ll see how they’re related.