Were Ronnie Van Zant and Mick Jones both lead singers of a band?
yes
Title: Ronnie Van Zant
Passage: Ronald Wayne Van Zant (January 15, 1948 – October 20, 1977) was an American lead vocalist, primary lyricist, and a founding member of the Southern rock band Lynyrd Skynyrd.  He was the older brother of two other rock vocalists: current Lynyrd Skynyrd lead vocalist Johnny Van Zant, and Donnie Van Zant, the founder and vocalist of 38 Special.  He was the father of singer Tammy Van Zant, and cousin of musician Jimmie Van Zant.
Title: Mick Jones (The Clash guitarist)
Passage: Michael Geoffrey "Mick" Jones (born 26 June 1955) is a British musician, singer and songwriter best known as the lead guitarist, co-lead vocalist, cofounder and songwriter for The Clash until his dismissal in 1983.  Afterwards, he formed the band Big Audio Dynamite with Don Letts.  Jones has recently played with the group Carbon/Silicon along with Tony James and has toured the world as part of the Gorillaz live band.  In late 2011, Jones collaborated with Pete Wylie and members of The Farm to form The Justice Tonight Band.
Title: Johnny Van Zant
Passage: John Roy "Johnny" Van Zant (born February 27, 1959) is an American musician and the current lead vocalist of Southern rock band Lynyrd Skynyrd.  He is the younger brother of the late Lynyrd Skynyrd co-founder and former lead vocalist Ronnie Van Zant, and of the 38 Special founder, Donnie Van Zant.
Ronnie Van Zant Mick Jones (The Clash guitarist)