The Duchess of Sussex broke contact with her father last year, telling him she and the authorities knew he had abused young girls, the understands.
Sources close to the duchess said Meghan warned Thomas Markle in a letter that he would never meet his grandchildren.
It is understood the letter was sent to Markle, 82, while he was in hospital in the Philippines after having his leg amputated.
It has been reported that images of child sexual abuse allegedly belonging to Markle had been found in his former home in the Philippines and UK police in 2019 told Meghan about allegations of child sex abuse against her father. Markle, who is based in the US, denies possessing any such images and claims of abuse.
Meghan has been estranged from her father since 2018. He pulled out of his daughter’s royal wedding that year, citing ill health.
The letter sent by in 2025 appears to be the end of what has been a troubled relationship between father and daughter.
It is understood details of the letter, first reported in the Sun on Sunday, external, include Meghan telling Markle that he would never meet his grandchildren, Archie and Lillibet, with Meghan making it clear she would never contact her father again.
She also apparently told her father that authorities were aware of the claims made against him.
Philippines officials have confirmed they are investigating the allegations about Meghan’s father, telling the on Friday that its anti-human trafficking and child sexual exploitation task force was investigating the matter.
Philippines Interior Minister Jonvic Remulla separately said national police had secured Thomas Markle’s computer and would carry out a digital forensic examination.
Meanwhile, Thomas Markle has given an interview to the Mail on Sunday, external in which he acknowledged paying for sex in the Philippines but denies sleeping with underage girls and ever possessing child abuse images.