Another Saudi prince has gone missing in suspicious circumstances, fueling speculation that the royal family is kidnapping its own defectors abroad and bringing them home against their will. Prince Sultan bin Turki was traveling to Cairo on Feb. 1 when he vanished, the Guardian reported Tuesday. He is the third royal family member reported to go missing in recent years. 

Prince Sultan, who has security guards watching over him 24 hours, had been involved in high-profile legal proceedings against the Saudi government over his alleged abduction and forcible repatriation from Switzerland in 2003. He was last seen when he and his entourage boarded a Saudi plane in Paris bound for Cairo, where he was expected to visit his father, King Salman’s elder brother, who lives there. Prince Sultan is one of hundreds of grandsons of Saudi Arabia’s first king, Abdulaziz ibn Saud. His father, Prince Turki, has lived in exile in Cairo and the U.S. for many years since clashing with the family. 

“There was a Saudi plane with a flight plan to Cairo, but the plane did not fly to Cairo,” said an associate of the prince who was with him in Paris. “This airplane had a Saudi flag on the tail. This plane came from the kingdom.”

Another friend who was waiting in Cairo for Prince Sultan told the Guardian: “Last call we had he was laughing and said as a joke, ‘I am supposed to come to Cairo this week by royal aircraft. If you didn’t find me they have taken me to Riyadh. Try to do something.’”

Two other high-profile royal defectors, Prince Turki bin Bandar bin Mohammed bin Abdurahman al-Saud and Prince Saud bin Saif al-Nasr bin Saud bin Abdulaziz al-Saud, have gone missing in recent years. All three men were critical of the Saudi government, the Guardian reported.

Prince Turki bin Bandar was a Saudi police officer before he defected to France. He applied for political asylum in Paris, where he became an advocate for nonviolent political reform in Saudi Arabia and vowed to write a tell-all book. He was last heard from in July 2015. Soon after that, he was slated to travel to Morocco for business and then disappeared, the Guardian reported. 

“Someone gave Turki bin Bandar the impression Morocco was safe, so he went there to do some business and the Moroccan government took him and gave him to the Saudis,” a member of a Saudi opposition group told the Guardian.

Prince Saud bin Saif al-Nasr bin Saud bin Abdulaziz al-Saud, meanwhile, became known as a critic of the regime on Twitter in March 2014. He alleged that billions of dollars worth of Saudi aid to Egypt had been embezzled under the late King Abdullah. In September 2015, he called for the removal of the king, his great-uncle. A few days later, he also disappeared, fueling social media accusations that he had been kidnapped.

“Saud bin Saif was approached by a Russian-Italian business consortium. They sent a private jet to take him to a meeting he thought was in Italy,”a Saudi friend of the disappeared princes told the Guardian. “He ended up inside the country.”

Some of the family feuding can be traced back to the lack of a clearly defined succession process in place, the Washington Post reported in 2014. Saudi Arabia's King Salman is expected to hand over the crown to his son, Prince Mohammed, which would deny the throne to his brothers, the remaining sons of the kingdom's founder, and their children.

Saudi Arabia was established as an absolute monarchy in 1932. The throne has passed from the founder, King Adbulaziz, to his son Saud, then to his brothers Faisal, Khalid, Fahd, Abdullah, then Salman, who became king on Jan. 23, 2015. Salman reportedly wants to make his son king while he is still alive to ensure his offspring will not be driven out of power.

Starting with Prince Sultan's alleged kidnapping attempt in 2003, few details have emerged about who is behind the apparent disappearances. 

“There are a lot of questions. What planes were there? Who was flying them? What were their flight paths? When did they arrive? How many from Saudi Arabia? How much in advance of Prince Sultan’s visit were they there preceding his abduction?” Prince Sultan's lawyer, Clyde Bergstresser of Bergstresser & Pollock PC in Boston, said of the 2003 repatriation attempt in December.