Complex sentence: Members Cass Elliot and Denny Doherty would become one-half of The Mamas & the Papas (who told the story of The Mugwumps in their song "Creeque Alley"), while John Sebastian and Zal Yanovsky would form The Lovin' Spoonful.
Split into simpler sentences: Members Cass Elliot and Denny Doherty would become one-half of The Mamas & the Papas, who told the story of The Mugwumps in their song "Creeque Alley". John B. Sebastian and Zal Yanovsky would form The Lovin' Spoonful.