Matthias may have been the brother of Simon Klee who lived in Laubach and died between 1720 and 1722. When he died the church records described him as Matthias Klee senior, i.e., the elder.

Source: Records of the Catholic church in Masburg.
Peter Bauer indicates that Maria Katharine’s family name was probably Steffes in light of the wedding dispensation of Franz Schmitz and Katharine Heinen in 1778. Katharine Heinen was the daughter of Anna Maria Klee and Johann Heinen, and the granddaughter of Mathias Klee and Maria Katharine (Steffes?). Franz Schmitz was the son of Peter Schmitz and Maria Margarete Steffes and the grandson of Johann Steffes and Anna Barbara.