Thomas Markle, the father of Meghan, Duchess of Sussex, has appeared in court after being charged over possession of child sex abuse material.
Markle was arrested on a federal complaint alleging he held images that show child sex abuse, the US Department of Justice (DoJ) said.
The 82-year-old was arrested in Florida after the FBI searched two Los Angeles-area storage units he rented for almost 20 years.
He is charged with one count of possessing indecent images of children, the US Department of Justice (DoJ) said. Markle has previously denied allegations of possessing images of child sex abuse, calling them "sick lies".
Markle's court hearing lasted for 30 minutes, and the charges were laid out against him by federal prosecutor Courtenay Derry, according to the BBC's US partner CBS News.
He was brought into court a wheelchair, escorted by two US Marshals. Markle was wearing black trousers and a black t-shirt.
The court ordered Markle to submit to home detention at his assisted living facility in Florida and electronic monitoring.
No plea was taken during the hearing, and an arraignment date in California will be determined in due course, a joint statement from the DoJ and the US Attorney's Office Central California said.
The Duke and Duchess of Sussex have not commented on Markle's arrest.
FBI director Kash Patel said authorities "moved quickly" when arresting Markle.
"Mr Markle allegedly targeted innocent children and sought to steal their innocence through his criminal actions," Patel said.
He added that the FBI would "use every single resource at our disposal to protect innocent kids – any predator who targets children will have zero safe haven in this country or anywhere they try to hide".
Markle was arrested after the FBI, acting on warrants, searched storage units in LA registered to him which he had rented since 2008, with the last payment being made in October this year.
Inside the units the FBI says agents seized about 78 items, including film negatives, slides and books that they allege contained child sex abuse material.
Witnesses "positively identified" Markle in two of the images believed to contain child sex abuse material.
In those images, the man pictured "appears to be in the age range of 30s to 40s", which suggests the alleged abuse dates back decades as Markle is currently 82 years old.
Last month, police in the Philippines obtained a warrant to examine devices allegedly removed from Markle's former home in the country.
Four boxes of material, including computers, phones, hard drives and old video tapes, were handed to officers by Meghan's half brother Thomas Markle Jr.
Markle Sr moved to the Philippines last year after he had a series of strokes, and lived in Cebu until May. He was then reportedly living in a Florida rehabilitation centre learning to walk again after having his leg amputated.
In October, London's Metropolitan Police confirmed that it had received a letter in 2019 making a "number of claims" relating to Markle Sr.
The Met said information contained in the letter, which related to allegations against Meghan's father outside the UK, was passed on to the office of the Duke and Duchess of Sussex, but it did not share it with other law enforcement agencies.
The force has since voluntarily referred itself to the Independent Office for Police Conduct (IPOC) over its handling of the letter.
In a statement released in October after the allegations against Markle Sr emerged, the Duchess of Sussex said: "I am deeply distressed at the news that has come to light in the last 24 hours, and my thoughts are with any children who may have been harmed."
Meghan has been estranged from her father since 2018. The BBC understands she broke contact with him last year.
