The phrase "true descendants" refers to people who are directly related to an ancestor. It means that they are the real and authentic descendants of that particular person. Full definition
Sometimes business decisions got ta get made when the only true descendant of whatever basketball planet LeBron came from is coming right at you. (sbnation.com)
True descendants of Abraham would gladly have opened their minds and hearts to Abraham's Messiah. (religion-online.org)
Moreover, a promise was given him, that he would be the father of many nations; the promise was given to him and to his descendants, and his true descendant was the Christ who was to come. (religion-online.org)