Robin Gibb, whose soaring vocals formed part of the unique Bee Gees sound, has died at the age of 62, leaving Barry as the sole surviving member from the band of brothers.
The high-pitched close harmonies, sharp songwriting and disco-defining sound of elder brother Barry, Robin and his twin brother Maurice made them one of the biggest-selling groups of all time.
Robin lost his battle against cancer of the colon and the liver on Sunday, a month after confounding doctors by emerging from a coma after suffering pneumonia.
He underwent surgery in August 2010 for a blocked intestine -- the same condition that killed Maurice in 2003 -- but a tumour was found and he was diagnosed with cancer.
The singer looked gaunt in his last few months as he struggled against the relentless disease.
Andy Gibb, their younger brother who was not in the Bee Gees, died in 1988 from cocaine addiction.
"I sometimes wonder if all the tragedies my family has suffered -- like Andy and Maurice dying so young and everything that's happened to me recently -- is a kind of karmic price we are paying for all the fame and fortune we've had," he told The Sun newspaper in March.
Robin enjoyed a musical career spanning six decades, from humble beginnings in the 1950s singing with his brothers in cinemas, to his recent first classical venture, "The Titanic Requiem", penned with his son Robin-John.
Gibb was too ill to attend the April 10 premiere, where he had been due to perform the song "Don't Cry Alone".
"It's not about how complicated music is; it's about how simple and relative to the human spirit it is," Gibb said on his new composition.
The singer and his wife-to-be Molly Hullis survived the 1967 Hither Green rail crash in southeast London that killed 49 people.
"I do think it is easier for me to walk in the shoes of the people who were on the Titanic," he wrote in The Mail on Sunday newspaper in January.
"I know what it is to live through a mass disaster... it haunts me to this day."
Robin Hugh Gibb was born on December 22, 1949 on the Isle of Man, the British crown dependency, about half an hour before Maurice.
Soon after the twins were born, the Gibb family moved to Manchester, northwest England, and then to Brisbane in Australia in 1958.
The Bee Gees soon became child stars and had their first hit in 1963, "The Battle of the Blue and Grey", performed on national television.
"We used to say that we were one soul in three bodies. We worked with such spirit between us, able to read each other's thoughts when we wrote together," Robin said.
The trio returned to Britain in 1967 where they soon had several more successes, including the UK number one "Massachusetts".
"How Can You Mend a Broken Heart", the group's first US number one, along with "Jive Talkin'", "Nights on Broadway" and "You Should be Dancing" established them as big stars.
But the disco soundtrack "Saturday Night Fever" (1977), which sold more than 40 million copies, was their biggest success. One of the best-selling albums of all time, its songs included perennial favourites "Stayin' Alive", "Night Fever" and "How Deep Is Your Love".
They wrote hit songs for others including Diana Ross ("Chain Reaction"), Barbra Streisand ("Woman In Love"), Kenny Rogers and Dolly Parton ("Islands In The Stream") Dione Warwick ("Heartbreaker") and Frankie Valli ("Grease").
Their last studio album was the 2001 record "This Is Where I Came In" and the group has notched up more than 200 million record sales.
Robin mostly sang lead in the 1960s, while Barry's falsetto took the foreground in their 1970s disco period.
The Bee Gees were made Commanders in the Order of the British Empire -- one step below a knighthood -- in 2004.
Robin Gibb was a friend of former British prime minister Tony Blair, who was criticised for taking "freebie" breaks with celebrity pals after holidaying at the singer's Miami mansion in 2006.
He appeared on a charity version of "Islands In The Stream" which topped the British charts in 2009, making the Gibbs the first songwriters to pen number UK ones in five successive decades.
Gibb was president of the International Confederation of Societies of Authors and Composers, which works towards increased protection of creators' rights.
He is survived by his wife Dwina and three children.
Gibb married Hullis in 1968 and the couple had two children: Spencer, born in 1972, and Melissa in 1974. They divorced in 1980. Robin-John was born to second wife Dwina in 1983.