Family #142 in the 1798 Grimm census.
Family #296 in the 1834 Grimm census.
At the time of the 1798 census, he was working in Anton (Sebastyanovka). In the 1834 census, there is no mention of a wife or children. It is very possible he remained single and had no heirs. Upon his death in 1819, his younger brother Johann Heinrich Menzer became head of household #296.
Head of the Household Mattias Menzer, age 40 in 1816, deceased 1819
Brother Johann Heinrich Menzer, age 44
Wife of Brother Anna Regina Menzer, age 40
Child #1 Barbara Menzer, age 8
Child #2 Katharina Christina Menzer, age 5
Child #3 Charlotta Menzer, age 6 months
↑The 1775 and 1798 Census of the German Colony on the Volga, Lesnoy Karamysh, also known as Grimm; Published by the American Historical Society of Germans from Russia, Lincoln, Nebraska, USA; Published date: 1995; family #142 in the 1798 census, Johann Just Mentzer, age 21.
↑1834 Census of Grimm in the District of Saratov, Russia, dated 2 February 1835; Translated by Brent Mai, Concordia University, Portland, Oregon; Published by Dynasty Publishing, Beaverton, OR, USA; Published 2011; page 82, family #296.