When Johann Henrich Mertz was born in December 1675, in Frankenhausen, Dieburg, Starkenburg, Hessen, Germany, his father, Johann Konrad Marth Martz, was 35 and his mother, Catharina Klippel, was 30. He married Anna Margaretha Elisabetha Poth on 10 June 1704, in Ober Ramstadt, Darmstadt, Starkenburg, Hessen, Germany. They were the parents of at least 5 sons and 5 daughters. He died on 24 June 1750, in his hometown, at the age of 74.