Paul McCartney is mourning the loss of his brother-in-law John Eastman -- older brother of his late first wife, Linda -- who died Thursday of pancreatic cancer at age 83, according to U.K. newspaper The Sun.

"My dear brother-in-law, John Eastman, has passed away," the former Beatles legend writes in a tribute posted on his official website. "Having known each other for over 50 years it is an extremely sad time for me, and our families."

McCartney continues, "John was a great man. One of the nicest and smartest people I have had the good luck to have known in my life. ⁠Not only did he help me massively in my business dealings as my lawyer but as a friend he was hard to beat."

Sir Paul adds, "His sense of humour always shone through in everything he did and his devotion to his family was supreme. ⁠We had so many fun times together through the years, but when the time came to be serious, he was unbeatable."

The note concludes, "[W]ords can hardly describe his passion for life and our affection for this amazing man. He will be sorely missed but always held dear in the hearts of those of us who knew and loved him. See ya Johnny!"

Accompanying the message is a photo of McCartney and Eastman smiling as they do yoga poses together.

John Eastman and his late father, Lee, were both lawyers who helped guide McCartney through his legal separation from his fellow Beatles during the band's breakup and also advised Paul on some of his lucrative business endeavors, including his investment in music publishing.

Paul wed Linda Eastman in March 1969, and the couple remained married until Linda's death in April 1998 at age 56.

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