Marvin Isley, bassist for the Isley Bros. during their hit-making funk resurgence of the ’70s, died June 6 in Chicago. He was 56, and had suffered from diabetes since the late ’90s.With his guitarist sibling, Ernie, Isley joined elder brothers Ronald, Rudolph and O’Kelly in 1969; the Cincinnati-vocal act had already scored such indelible R&B hits as “Twist and Shout” and “This Old Heart of Mine.” At the T-Neck label, the Isleys vaulted back to the top of the R&B charts with such hits as their cover of Stephen Stills’ “Love the One You’re With” (No. 3, 1971), “That Lady” (No. 2, 1973), “Fight the Power” (No. 1, 1975) and “The Pride” (No. 1, 1977). In 1985, he joined brother Ernie and keyboardist Chris Jasper in Isley, Jasper, Isley, which notched the No. 1 R&B smash “Caravan of Love.” He rejoined the Isleys from 1991 until 1997, when health issues forced him to retire. Survivors include his brothers Ron and Ernie.