The post came hours after his ex-girlfriend Kim Turnbull addressed rumors that she was involved with his older brother.
The 22-year-old model and former soccer player shared a simple request for the masses via an Instagram Stories post on Monday, June 16.
"Be nice to people and don't tell unnecessary lies," he wrote.
His words were shared over a still of Audrey Hepburn and Gregory Peck in the 1953 romantic comedy Roman Holiday.
The image also showed the words from Hepburn and Peck's conversation: "What the world needs is a return to sweetness and decency."
Romeo's post came hours after his ex-girlfriend, model and DJ Kim Turnbull, shared a statement to her Instagram Stories denying rumors that she was once romantically linked to his older brother, Brooklyn Beckham.
"I've avoided speaking on this topic to prevent adding fuel to the fire, however it's come to the point where I feel the need to address it so I can move on," Kim wrote. "I will not continue to receive harassment or be embarrassed on the basis of lies, to fit a certain narrative."
She continued, "I have never been romantically involved in ANY capacity at ANY point with the person in question. Nothing between us has occurred further than a school friendship at age 16. I would like to remove myself from the ongoing conversation & set the record straight for the sake of everyone involved."
Though Romeo and Brooklyn's younger brother, Cruz, previously told a commenter in an Instagram post that "Brooklyn and Kim never dated," rumors have still circulated about the alleged romance.
Speculation also circulated that there were issues within their inner circle when it came to Kim being present at events where Brooklyn, 26, and his wife, Nicola Peltz. 30, attended.
"Brooklyn didn't want to be in the same room as her, and he told his dad that. But David opted to have Kim there over Nicola," a source told PEOPLE of why Brooklyn and Nicola skipped David Beckham's 50th birthday bash in May.
Another source added, "Brooklyn and Kim know each other from the past, and his family knows he's not comfortable around her."
Amid the alleged family drama, Romeo has continued to show support for his family.
On June 13, he shared how proud he was of his famous father after the Inter Miami CF co-owner was named for knighthood by King Charles earlier that same day.
“So so proud of you 🤍🤍🤍🤍,” he wrote on an Instagram Stories photo of himself and his father smiling together in a blurry image.