Rudolph Isley, a founding member of the legendary R&B group The Isley Brothers, has died at the age of 84.

The iconic singer passed away in Illinois on Wednesday, according to TMZ. It’s believed he suffered a heart attack but details of his cause of death were not immediately made known. The Daily News reached out to an Isley Brothers rep for comment.

As a teenager, Rudolph Isley began performing gospel music with his brothers O’Kelly, Vernon and Ronald in their native Cincinnati. They soon began touring around the eastern United States, performing in a variety of churches.

Following the tragic death of Vernon, who was killed after he was hit by a car while riding his bike at the age of 13, the group initially disbanded. However, they eventually regrouped and, as a trio, relocated to New York City to pursue other genres including pop, R&B and soul.

After a few years of only regional success, the band signed with RCA Records and had their first mainstream hit with 1959’s “Shout,” which Rolling Stone later ranked as one of the The 500 Greatest Songs of All Time. They followed that success with their cover of “Twist and Shout,” which spent 11 weeks at No.1 on the Billboard Hot 100 chart.

The group went on to produce additional hits like “This Old Heart of Mine” and “It’s Your Thing” under their own record company, T-Neck Records, and later with Motown. However, Rudolph exited the group in 1989 to fulfill his dream of becoming a Christian minister.

He reunited with his brothers from time to time throughout the years, including in 1992 when they were inducted into the Rock & Roll Hall of Fame.

The news of Isley’s death comes amid a legal battle between him and his younger brother, Ronald, over The Isley Brothers trademark.

Earlier this year, Rudolph filed a lawsuit against Ronald, claiming that since the 1986 death of their brother O’Kelly, the two have been the equal co-owners of the group’s intellectual property, therefore Rudolph was seeking his “rightful 50% share of all results and proceeds.”

Ronald meanwhile argued that the “Isley Brothers” trademarks were the property of those who had actually been using the name, and that his brother has not performed with the group since the late 1980s.

Rudolph, who had been married wife Elaine Jasper since 1958, leaves behind three children and multiple grandchildren.