We have a Check for Duplicates feature in Family Tree Builder that runs a duplicates check on your family tree, locating individuals that may be duplicates.
To use it, open your tree in Family Tree Builder.
Click on the ‘Tools’ menu in the upper menu bar and select ‘Check for duplicates’.
The check will run on your tree. You can then edit your tree accordingly.
To merge duplicates, please read this FAQ post: How do I merge duplicates in my Family Tree Builder project?