He called her "shallow" in the Big Brother VIP trailer, and they haven't spoken for ten years, so it's safe to assume that Thomas Markle Jr. and his half-sister Meghan Markle are well and truly estranged.
Meghan's fraught relationship with her half brother along with the rest of her dad's family has been well publicised in the media.
In her interview with Oprah, she revealed she hasn't spoken to her father, Thomas Markle, since he staged paparazzi photos before her wedding.
While we are aware of the 40-year-old's relationship with her father, we know less about her connection with half brother, Thomas Markle Jr.
From the looks of the Big Brother VIP trailer, it seems Thomas will have plenty to say about the Duchess.
In anticipation of Thomas' appearance on our screens, we take a look into his complex relationship with half-sister Meghan Markle.
The pair are half siblings through their father, Thomas Markle.
The unauthorised biography, Meghan: Hollywood Princess by Andrew Morton, claims Meghan's mum Doria met her father, Thomas, on the set of American series General Hospital.
Doria was training as a makeup artist, and Thomas worked as the show's lighting director, and after briefly dating, they decided to get married in 1979. In 1981, the couple welcomed their only child together - Meghan Markle.
Thomas was already the father of Thomas Jr. and Samantha Markle, from his first marriage to Roslyn Loveless.
For the first two years of her life, Meghan lived with her parents and half-siblings Thomas Jr. and Samantha in Woodland Hills, LA until her parents separated. Their divorce was finalised in 1988.
Growing up, the future royal lived predominantly with her mum but spent weekends with her dad.
In a 2017 Vanity Fair interview, Meghan spoke about how well her parents got a long - despite the split.
"What's so incredible, you know, is that my parents split up when I was two, [but] I never saw them fight," she told the publication.
"We would still take vacations together. My dad would come on Sundays to drop me off, and we'd watch Jeopardy! eating dinner on TV trays, the three of us. . . . We were still so close-knit."
During her Oprah interview earlier this year, Meghan set the record straight on her relationship with Samantha and Thomas Markle Jr.
"I grew up as an only child, which everyone who grew up around me knows, and I wished I had siblings. I would have loved to have had siblings - that's why I'm so excited to be pregnant, so that Archie has someone," the former Suits star explained.
Despite a conflict-free childhood, something changed between their family dynamic during their adult years, which has led to a long-term estrangement between Thomas and Meghan.
Both sides have stayed tight-lipped about the true reason behind their split, but in an interview with Bild, the 55-year-old revealed some telling details.
He claims the last time he saw his sister was in 2011 at their grandmother's funeral, around ten years ago.
In 2018, Thomas Markle Jr. slammed his half-sister over her decision not to invite him to her wedding to Prince Harry.
Speaking with The Mirror, Thomas revealed his anger around his snub and accused Meghan of hurting him despite how close they were as children.
"I'm not bitter, just baffled. It's hurtful given how close we once were," he shared.
"I'm confused and a little distraught because here is a person knowing the position she's in and knowing the scrutiny she's under and yet she has forgotten her flesh and blood."
Bizarrely, Thomas appears to ebb and flow between enraged and sympathetic towards his half-sister.
In his interview with Bild, he accused Meghan of changing once she became a royal.
"Nobody recognises the Meghan we are seeing right now," he said. "I have seen her bully people before in the past and get her way, no matter what."
But after her interview with Oprah, he empathetically spoke to Today about how he found her recounts of bullying and racism during her life as a royal harrowing.
"It's a little heart-wrenching to hear stories like that coming from your sister," he said.
"I think it is kind of hard to make something like that up, especially on national television."
"To be faced with an issue like that pertaining to the colour of your son's skin would be horrific for anybody to deal with. You know my heart goes out to her actually, honestly," he continued.
He also revealed to Today that he has hopes to reconcile with Meghan.
"I really, really hope that some day when all of this goes away we can all get together without the press and just have a normal get together and brush all this under the carpet and go on," he told Today.
"None of the family has had a bad bone to pick with her, ever, and it would be nice to - especially for my father."
However, from the look of that explosive Big Brother VIP trailer, it seems Thomas' tone towards Meghan has once again turned sour.
He claims in the video that he spoke to Prince Harry and told him, "I think she's going to ruin your life. She's very shallow."
Thomas was married to Tracy Dooley for 11 years, and they have two sons together called Thomas and Tyler.
His ex-wife Tracy has claimed her ex-husband has issues with alcohol.
Indeed Thomas has had many the run-ins with the law over the years. At the start of 2017, Thomas Jr. was arrested in Oregon after a drunken fight saw him allegedly threaten his then girlfriend, Darlene Blount, with a gun.
Darlene and Thomas became engaged in 2019 but have since split.
According to The Sun, the reality TV star works as a window fitter and lives in Grants Pass, Oregon.