Lothar Francis was born in Steinheim am Main in 1655 to Count Philip Erwin of Schönborn. He was a nephew of John Philip of Schönborn, Archbishop of Mainz from 1647 until 1673, and a grand nephew of George Frederick of Greiffenclau, Archbishop of Mainz from 1629 until 1629. Furthermore he was an uncle to the influential Schönborn-Buchheim branch which included John Philip Francis, Frederick Charles, Hugh Damian and Francis George.