Peter Tork’s sibling didn’t say where or how he died, according to The Washington Post.
The star was diagnosed with a rare form of cancer affecting his tongue back in 2009.
The Monkees were famous for their hit songs I’m a Believer, Pleasant Valley Sunday and Daydream Believer.
A post on behalf of Peter’s friends, family and colleagues was posted on his official Facebook page to announce the news this afternoon.
It read: “It is with beyond-heavy and broken hearts that we share the devastating news that our friend, mentor, teacher, and amazing soul, Peter Tork, has passed from this world.
“As we have mentioned in the past, the PTFB team is made up of Peter’s friends, family and colleagues – we ask for your kindness and understanding in allowing us to grieve this huge loss privately.”
They continued: “This page will remain open for your use in sharing your thoughts with your fellow fans and hopefully helping you through your own grieving journey, however the team will not be available for some time as we start to mend our own hearts and calm our minds.
“We want to thank each and every one of you for your love, dedication and support of our ‘boss’. Having you in our world has meant so very much to all of us.
“Please know that Peter was extremely appreciative of you, his Torkees, and one of his deepest joys was to be out in front of you, playing his music, and seeing you enjoy what he had to share. We send blessings and thoughts of comfort to you all, with much gratitude ~ptfb team.”
Peter shot to fame as a member of American rock and pop band, The Monkees, who were active between 1966 and 1971.
The quartet, which featured Peter, Micky Dolenz, Michael Nesmith and Davy Jones, were one of the most successful groups of all time having sold more than 75 million records worldwide.
Back in 2009, Peter reported on his website he had been diagnosed with adenoid cystic carcinoma, a rare form of head and neck cancer.
He explained: “It’s a bad news / good news situation.
“It’s so rare a combination (on the tongue) that there isn’t a lot of experience among the medical community about this particular combination.
“On the other hand, the type of cancer it is, never mind the location, is somewhat well known, and the prognosis, I’m told, is good.”
Peter reportedly underwent radiation treatment and extensive surgery to shrink the tumour.
Upon hearing the news of Peter’s death, tributes have poured in for the musician.
One person wrote on Twitter: “Sad news about the Monkees today. RIP Peter Tork.”
Another said: “I loved The Monkees. Head is an underrated classic. RIP Peter Tork.”
A third commented: “I’m devastated. RIP Peter Tork of the Monkees. He was 77. Many thanks for the decades of great music and laughs. #petertork.”