Question: "What is the Desposyni / Rex Deus?"
Answer: Desposyni is a name given to the blood-relatives of Jesus through His mother, Mary. They are believed by some to have had a large part in the leadership of the Church in its formative years up through the 4th century, at which time references to the Desposyni seem to have disappeared. Many attribute this to violent persecution against Jewish Christians, Desposyni in particular. There are some who believe that Jesus Christ married Mary Magdalene and had children with her, whom are also called Desposyni. It is believed that this dynasty exists yet today and has played a large role in world government and religious leadership.
Rex Deus also attributes its lineage to the supposed marriage of Jesus and Mary, but also goes back to King David and, even further, to the High Priest Aaron, Moses' brother. According to theorists, the Rex Deus have kept their bloodline pure throughout the last few thousand years and are supposedly custodians of the "true" secrets of Judaism and Christianity.
The Desposyni, as being blood-descendants of Mary, Jesus' mother, are historical fact. They are mentioned in historical records through the fourth century, A.D. However, claims that Jesus married Mary Magdalene and had children with her are clearly untrue, and should be immediately discounted. Nowhere in Scripture is it stated that Jesus took a wife, let alone that it was Mary Magdalene. It cannot even be insinuated using biblical text. Every mention of Mary Magdalene in Scripture negates every assumption that there was a sexually intimate relationship between her and Jesus. This twisted view cannot even be supported by non-canonical gospels which reference Mary Magdalene, such as the Gospel of Thomas, the Gospel of Peter, or even the Gospel of Mary.
The marriage of Jesus to Mary Magdalene is merely a man-made farce, a tool created to further the work of fringe researchers and conspiracy theorists. The ideas behind the Desposyni and Rex Deus arise from mankind's penchant for solving mystery and for exposing the unknown. Their feeling is there must be an explanation for everything that happens in world history, and what is unknown does not suffice. So, theories are created by twisting historical facts. Farces are introduced as truth, and a few grasp onto this "truth" and take it to the next level in attempts to expose mystery and subterfuge. Secrets contain knowledge, and knowledge power, and will forever ever be an enticement. We who are believers, though, understand that there is only one Truth by which all mysteries are judged—the very Word of God (2 Timothy 3:16-17).