Thomas Kingston, Lady Gabriella Kingston’s husband, died from a “traumatic head wound”, an inquest has heard.
A gun was found near his body in an outbuilding at his parent’s home in the Cotswolds.
Aged 45, Mr Kingston was the son-in-law of Prince and Princess Michael of Kent. He died on 25 February.
The inquest into his death opened on Friday at Gloucestershire Coroner’s Court.
His death was not being treated as suspicious, and no-one else was involved.
Mr Kingston married Lady Gabriella in 2019 in a ceremony attended by Queen Elizabeth II.
In a statement issued by Buckingham Palace shortly after Mr Kingston’s death, Lady Gabriella, 42, described her husband as an “exceptional man who lit up the lives of all who knew him”.
King Charles and Queen Camilla sent their “most heartfelt thoughts and prayers” to his family.
Senior coroner Katy Skerrett said in the lead up to his death, Mr Kingston had lunch with his parents before his father went out to walk their dogs.
When his father returned, Ms Skerrett told the inquest, Mr Kingston was no longer in the house.
“After approximately 30 minutes his mother went to look for him,” Ms Skerrett said, then his father had to force entry on a locked outbuilding – as there was no reply from Mr Kingston.
His father then found his 45-year-old son “deceased with a catastrophic head injury” with a gun “present at the scene”, Ms Skerrett added.
Mr Kingston was a director at private equity firm Devonport Capital. He had previously worked with the diplomatic missions unit of the Foreign Office in Baghdad, Iraq, where he was involved in securing the release of hostages.
He married his wife, Lady Gabriella, at Windsor Castle’s St George’s Chapel. Prince Philip and Prince Harry were also among the royals to attend the service.
Lady Gabriella is a part of the Royal Family but is not a working royal.
She and Mr Kingston’s family are being supported by the royal household.
Her father, Prince Michael, aged 81, is a grandson of King George V and first cousin of the late Queen Elizabeth II.
No funeral plans have been announced.
On Tuesday, Prince and Princess Michael attended a Windsor service for the late King Constantine II of Greece – who, as Lady Gabriella’s godfather, had attended her wedding to Mr Kingston.