This is not an individual family tree. We all share the same tree, so if one person is in your family and in mine at the same time we share that relationship and our trees "merge" on that relative. Easier to understand with distant ancestors, some of my ancestors are my grandfather's and my grandmother's at the same time, so no use having them appear twice, in the same way, some of your ancestors may be mine as well, you don't have to do all the job, someone has done it already on some branches, all you have to do is merge with what has already been done. This is the good thing with this way of treating genealogy : we all build our family tree together. The bad thing, too, because sometimes your get ten times the same person to merge.
