The late singer - who died in May aged 62 after losing his battle with cancer - says his brothers Barry and Maurice had a bond stronger than blood and were united against the world to make the best music they possibly could.
Writing some of his last words on the sleeve notes of the band's four-disc boxed set 'Mythology', Robin revealed: "It wasn't just because we were brothers that we did the things we did. We were like one soul in three bodies. We were thinking as one and a world unto ourselves. We strived to be original and were envious of anything that was great, but instead of resenting what was great or copying it, we wanted to be different, or to improve upon it.
"I always see our songs as "just us three brothers" having a good time. When I look back now, it is more about the journey, not the arrival."
The legendary pop trio - best known for the 'Saturday Night Fever' soundtrack, revered as a classic of the disco era - had been pioneering their music from 1958 and at the time just before his death, Robin felt their creative genius was just as strong as ever and they could still write a hit in record time.
He wrote: "To us, going into a studio to work was like a painter facing an empty canvas or an author starting with a blank page. We very rarely went into the studio with a complete song, but instead wrote in the studio because of the creative atmosphere.
"We have a love affair with creativity. Since I was eight years old, we have worked like this and have had fun with it. It was not for money; it was for pure pleasure."