Gary Goldsmith, aged 58, is the younger brother of Kate’s mother, Carole Middleton. He was a guest at Kate’s wedding to William, the heir to the throne, in 2011.
Goldsmith’s appearance on the show comes at a testing time for the royals after King Charles was diagnosed with cancer and Kate has been absent from public life while she recovers from abdominal surgery in January.
Goldsmith said in the show that Kate was “simply perfect”.
“The first time I met William, Catherine was cooking and William said ‘Hi, do you want a cup of tea’,” he said. “Very normal.”
During Monday’s launch episode as Goldsmith prepared to enter the house, host AJ Odudu wasted no time in asking him whether his royal niece would be tuning in.
He joked: “If she is, it will be behind a sofa, I guess’.
The businessman, who made a fortune in IT recruitment, said he wanted to “put the record straight” about his bad boy reputation.
But added: “Winding people up is probably my favourite hobby. Every part of me is just riddled with mischief and danger.”
“I’m an absolute nightmare to live with; there’s a reason why I’ve had four wives,” he added.
In 2017 Goldsmith was fined after he assaulted his fourth wife, Julie-Ann, in a drunken argument.
He joined 11 other celebrities including reality TV judge and music manager Louis Walsh and TV presenter Fern Britton in the Big Brother house, where they are constantly filmed.
Celebrity Big Brother has been revived by broadcaster ITV six years after it last aired on rival Channel 5.
