Wendt was born in Itzehoe, a small town in Holstein, then a Danish province, son of Joachim Matthias Wendt and his wife Christina, née Schlichting.
He settled in Itzehoe in 1907, where he pursued architectural and interior design projects.
After Gerhard I's death in 1290 his three younger sons partitioned Holstein-Itzehoe and Schaumburg into three branches, with Adolph VI the Elder, the third brother, getting Holstein-Pinneberg and Schaumburg south of the Elbe, the second brother Gerhard II the Blind getting Holstein-Plön, and the fourth Henry I receiving Holstein-Rendsburg.