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A native of San Antonio, Dan joined up with Willie in the late '60s and stuck with the country legend for decades, establishing himself as one of the pillars of the group.
"We are deeply saddened by the death of Family member Dan "Bee" Spears, longtime friend and bassist for Willie Nelson and Family," read an official statement on Willie's website.
"He was part of our family, it's a big loss," Willie's nephew Freddy Fletcher, a recording studio owner, told the American-Statesman. "He was basically the only bass player Willie ever really had. He was a great musician, a great guy; he was like a brother to me, and we're all really sad."
"He was just a sweetheart; he always had a hug for everybody," said Turk Pipkin, an author and filmmaker who was friends with both Dan and Willie. "They talk about the Family Band, and I think Bee really personified that."
Willie and his band are still scheduled to perform on Dec. 30 and 31 as part of Austin City Limits Live.