In 2020, a Saudi court jailed Omar and Sarah Al-Jabri for money laundering and conspiracy to escape the Kingdom unlawfully, charges they deny.
They were arrested in Riyadh while Jabri's son-in-law, Salem Almuzaini, was detained in Dubai and then flown to Saudi Arabia, the world's biggest oil exporter and close ally of the United States.
The governments of Saudi Arabia and the United Arab Emirates did not immediately respond to requests for comment.
Riyadh said previously all the applicable legal procedures were followed throughout the case, and they were accorded all of their rights, including representation by counsel. The charges on which the Jabri siblings were convicted of were not related to the case against their father, it said.
On 4 November, 2020, a Saudi court sentenced Omar to nine years' imprisonment and his sister received a 6.5 years term, without the opportunity to present or cross-examine witnesses.
The United Nations said Saudi Arabia should release Jabri's children and Almuzaini immediately and unconditionally.
It called on the United Arab Emirates to compensate and provide reparations to Almuzaini for his detention.
Jabri was long an aide to another Saudi Royal, Prince Mohammed bin Nayef, whom Crown Prince Mohammed bin Salman, or MbS, ousted as heir to the throne in a 2017 palace coup.
"Unable to communicate with their immediate family and having been disappeared to a secret location, Mr. Aljabri and Ms. Aljabri have reportedly suffered severe psychological torture," said the United Nations in an opinion.
"During this detention, Mr. Almuzaini was allegedly physically and psychologically tortured: he was beaten and lashed and held incommunicado, with Saudi forces denying him visits and contact with anyone outside of the prison."
In 2020, Jabri, who is living in exile in Canada, alleged in a lawsuit filed in a US court that MbS sent a team to kill him in 2018, but the effort was foiled by Canadian authorities.
In a 107-page lawsuit against MbS and 24 others filed in federal court in the District of Columbia, Jabri said the Crown Prince "dispatched a hit squad" to Canada in October 2018.
The alleged incident took place less than two weeks after Saudi agents murdered journalist, Jamal Khashoggi in the Kingdom's Istanbul consulate.
The Crown Prince's lawyers have rejected Jabri's allegations and said MbS has legal immunity in the United States as a foreign head of state. Dismissing the allegations in 2020, MbS's lawyer, Michael Kellogg, described them as "steeped in drama".