How did half of your family get duplicated? Did you import a GEDCOM, add a person normally, etc. As for deleting them, you cannot delete them if a branch of your family (or even one family member) is connected to the tree by them only. There are glitches with GEDCOMs where siblings whose parents aren't in the file get split off upon importing and are not connected to the family at all, though (I've experienced this myself), but I don't know if it is related to Family Echo or if they weren't specified as siblings in the GEDCOM.
