Marvin Isley, bass player and the youngest of the R&B group the Isley Brothers, died last Sunday at the age of 56 at Weiss Memorial Hospital in Chicago. The cause of the death was not confirmed.

Isley stopped performing in 1996 due to complications from diabetes. His physical challenges included a stroke, high blood pressure, the loss of both legs as well as the use of his left hand.

The Isley Brothers were already an established hitmaker, when Marvin joined the group in 1973. Although his bass playing added a distinctive element to the group’s sound, Isley left the group in the 1980s. He started the fledgling group Isley-Jasper-Isley but ultimately returned to the Isleys in the 1990s.

At one point, there were five Isley brothers in the group, including Marvin. Today, only Ronald Isley is touring regularly, after completing a three-year sentence in federal prison for tax evasion. The group’s hits included “Twist and Shout,” “Love the One You’re With,” “Between the Sheets,” and “It’s Your Thing.”

In 2000, Marvin settled a lawsuit against his siblings stemming from a dispute over money from the estate of his deceased brother, O’Kelly Isley, and also from a $7 million plagiarism award against Michael Bolton relating to the group’s 1966 hit, “Love Is a Wonderful Thing.”

In 2001, Marvin Isley revealed in an interview that he regretted spending decades ignoring his diabetes. “If I would have listened,” he reflected, “if I would have understood diabetes like I understood music, maybe these things wouldn’t have happened.”

Isley is survived by his wife Sheila, a son and two daughters. Funeral services were pending at press time.