Peltz Beckham said he had been subject to “endless attacks from my parents, both privately and publicly, that were sent to the press on their orders”.
He added that his younger brothers had also been “sent to attack me on social media, before they ultimately blocked me out of nowhere this last summer”.
Cruz Beckham, 20, said in December that their parents would “never unfollow their son,” in response to a Daily Mail story claiming they had done so.
“Not true. My mum and dad would never unfollow their son. Let’s get the facts right,” he wrote on Instagram.
“They woke up blocked as I did.”
Ex-England football captain Sir David and former Spice Girl Lady Beckham have two other sons and a daughter – Romeo, 23, Cruz, 20, and Harper Seven, 14.