Complex sentence: In the period of 1984 and 1985, the band member also became Nenad Cvetičanin, Predrag's brother, who joined the band while his own, Arnold Layne, was on hiatus.
Split into simpler sentences: In the period of 1984 and 1985, Nenad Cvetičanin, Predrag's brother, also became a member of the band. He joined the band while his own, Arnold Layne, was on hiatus.