Legacy Family Tree can help find "lost cousins" by producing a gendex.txt file when you are creating your website.
However, it seems most users are unaware of this function and its valuable usage.
A gendex.txt file only contains First Name, Surname, Birth Date, Place of Birth, Death Date, and Place of Death
along with the URL to each person on your website. You do not lose control of your family tree data with gendex!
To create the gendex.txt file with Legacy Family Tree, have your family tree open;
then click on; Internet; Create Web Pages; Other; then check the box beside "GENDEX genealogical index" as shown here -