Jimmy Buffett's younger sister battled cancer at the same time as the late singer and is "thunderstruck" that he's gone.

The ‘Margaritaville’ star was diagnosed with a rare form of skin cancer four years ago before the disease progressed to lymphoma – which was his cause of death on September 1 aged 76.

Laurie Buffett McGuane, 74, has revealed the pair's bond grew "closer" as she also battled pancreatic cancer and had treatment at the same time as her older sibling.

She told People: "When Jimmy found out [I had cancer] he brought the whole family and the dogs to Montana to be with me.

Jimmy and I became closer because of our cancers. We talked before and after our scans. We shared a club that nobody wants to join."

She admitted: "I am thunderstruck that Jimmy didn’t make it.”

Both tried to continue their lives as normally as possible.

Laurie - who is married to author Tom McGuane - explained: “I rode my horse during my treatments and tried to continue with my life the same way Jimmy has done."

Jimmy was devastated when he was forced to cancel his concerts.

Laurie added: “Jimmy wanted to perform the shows that he had to cancel.

“He brought joy to so many. I am very emotional now. When Jimmy was in the world, I felt safe. Even though I have Tom, it will be a whole new thing for me to be without my brother Jimmy.”

Laurie and their other sister Lucy - nicknamed Lulu - were by their brother's side when he passed.

Following his passing, she wrote on Instagram: “Lulu and I were just with Bubba [Jimmy]. We talked about our childhood where only siblings can relate. I told him I’ve known him longer than anyone on the planet. He smiled with those twinkling blue eyes and squeezed my hand.”

The musician had been in a hospice for a week before he died.

Sir Paul McCartney, 81, reportedly visited the Grammy nominee at his home to sing to him.

A statement posted on Jimmy’s social media accounts that announced his death read: “Jimmy passed away peacefully on the night of September 1 surrounded by his family, friends, music and dogs.

“He lived his life like a song till the very last breath and will be missed beyond measure by so many.”

Jimmy is survived by his wife, Jane Slagsvol, as well as daughter Savannah, daughter Sarah and son Cameron.

A string of stars honoured the musician and businessman with social media tributes.

Country star Kenny Chesney, 55, said on Instagram: “So goodbye Jimmy. Thanks for your friendship and the songs I will carry in my heart forever. Sail On Sailor.”

Sir Elton John, 76, hailed Jimmy as a “unique and treasured entertainer”.

The ‘Rocketman’ singer said: “Jimmy Buffett was a unique and treasured entertainer. His fans adored him and he never let them down.

“This is the saddest of news. A lovely man gone way too soon. Condolences to Jane and the family from David (his husband) and me.”