The Common Ancestor button in Genealogy Browser shows you when one individual appears more than one time in your tree.
The Common Ancestor Feature is simple to use:
1. Locate your toolbar at the top of your screen in Genealogy Browser.
2. Click on the Common Ancestor icon.
3. Look for blue boxes in your Starfield. A blue box means that individual appears more than once in your tree.
In the illustration below, Carroll appears twice. The blue box means he appears more than once. The blue line allows you to quickly find Carroll's other location. Carroll is Sanford Carroll's father, and he is Elizabeth Bartlett's grandfather. This means Sanford Carroll and Elizabeth Bartlett were uncle and niece before they were husband and wife.