67-year-old Gibb, who is due to play Dublin's 02 this September as part of his new Mythology Tour saluting his siblings, has said that the brothers were not communicating with each other in their last days together.
"That's the one biggest regret, that we didn't speak, we weren't really speaking very much to each other. We weren't being intimate in those last days of each of their lives."
Barry is the last remaining member of the band following Robin's death last year after a battle with cancer, Maurice's passing in 2003, and younger brother Andy, who died in 1988, aged just 30.
Gibb told The Guardian newspaper that Robin kept his illness secret from him for years. "Nobody was telling me anything," he said. "So I showed a picture of Robin in the papers to my doctor, because he didn't look well. My doctor said: 'Go and see him, he's got maybe six months.' I thought, Jesus. That's all my brothers."
"I'd noticed that when he was doing live shows, he'd started lowering all the keys he sang in, so that was another sign for me: there's something wrong, Rob, even if you're not telling me what it is.
"I just wanted to say to him: 'Why can't we let the Bee Gees … why can't we sit down and enjoy what's happened? Why can't the dream have come true? Why do we still have to chase this dream when it's really come true?' But him and Mo, they were just too restless."
He also revealed that the band were keen drugs dabblers in their early days but avoided LSD and stuck to majuana and occassional experimentation with mushrooms.