A furious Frank Stallone slammed the academy in a foul-mouthed tirade for snubbing big brother Sylvester in the best supporting actor category at this year's Oscars.
The Rocky star was widely backed to bag the prize following a Golden Globe award for his critically acclaimed turn as the boxer in Ryan Coogler's spin-off movie Creed.
But the statuette went instead to Britain's Mark Rylance for Bridge of Spies, in one of the biggest shocks of the gala ceremony at Hollywood's Dolby Theatre.
"The Academy should be ashamed of themselves. It's as clear as the nose on your face that Sly won. Mark who? It's total Hollywood bullshit," tweeted livid actor and musician Frank, 65.
The younger Stallone, warming to his theme, insisted that Rylance should have "been embarrassed" to supplant an actor who had done a "historic job" creating two cinema icons that have appeared in films spanning four decades.
Sly's underdog prizefighter turned world champion boxer Rocky Balboa spawned seven movies grossing an inflation-adjusted $1.7 billion in North America alone, while four Rambo films featuring irritable Vietnam vet John Rambo took in $674 million.
"Mark Rylance couldn't even comb his hair for Christ sake this is the 3rd time Sly's gotten ripped off Rocky, Copland and Creed. New Voters," Frank tweeted, although his brother was never nominated for 1997 crime drama Cop Land.
Stallone himself was in more magnanimous mood, posting a picture of himself on Instagram in his black and blue Oscar tuxedo winking at the camera, fist clenched in defiance.
"To all the 'real Rocky's' of the world, Please hang on to your dreams, NEVER GIVE IN, NEVER GIVE OUT, NEVER GIVE UP! thanks for the support," said the 69-year-old.
He later posted a screenshot of a smiling Rocky from Creed, assuring fans that he was "very happy" and urging them to "please understand my brother is so em motional (sic) because he is just very protective and only wants the best for me. Life is good!"
Stallone was last nominated for an Oscar 39 years ago as best lead actor and writer for Rocky.
A host of celebs rushed to ally themselves with Team Sly, including British media personality Piers Morgan, US actress Mia Farrow and Arnold Schwarzenegger, Stallone's co-star in action franchise "The Expendables."
"Sly, just remember, no matter what they say, to me you are the best, you were the winner. I'm proud of you," Arnie said in a video posted to Facebook.
Rylance, 56, was asked backstage how it felt to have outpunched Stallone but said he didn't take awards too seriously.
"I don't know, people come up and say things about competing as actors and I know it's necessary to make a show out of it," he told reporters, insisting he did not feel "better" than his fellow nominees.