The Duchess of Sussex's estranged brother Thomas Markle Jr. wrote an open letter apologizing for asking Prince Harry to call off their wedding

• Meghan Markle's brother Thomas has apologized for an open letter he wrote about the duchess in 2018.
• In the letter, he urged Prince Harry to call off the wedding and called Meghan "conceited."

Thomas Markle Jr. read an open letter in which he apologized to the Duchess of Sussex during Monday's episode of "Big Brother VIP Australia," according to The Independent.

Thomas, 55, is Meghan's estranged half brother from her father's side of the family. He has made multiple negative statements about his half sister through the years and previously urged Prince Harry to call off their 2018 wedding.

In a handwritten open letter published by In Touch in May 2018, Thomas criticized Meghan for not inviting her family to the wedding and called her a "jaded, shallow, conceited woman."

He also urged Harry to "put an end to this fake fairytale wedding before it's too late."

Speaking on the reality show "Big Brother VIP," Thomas said he was "sorry from the bottom of my heart" for the "awful, mean letter" he wrote before the wedding, The Independent reported.

"And I want both of you to know it did not come from the real person that I am but came from a very dark and hurt part of my heart. … I am not a mean person at all, and I have more love inside me to give than anything," he added.

Thomas added that the original letter had been written out of hurt upon learning that Meghan had described him as a "distant" family member, according to the publication.

"I was very hurt and confused because of the amazing bond and relationship we shared growing up together, and all I could do was put up a defense wall to protect my heart," he said, according to The Independent. "I know that it was very immature and wrong and I truly regret it."

Representatives for the Duke and Duchess of Sussex declined to comment when contacted by Insider.