Famiy #145 in the 1798 Grimm census.
Family #231 in the 1834 Grimm census.
Michael Engelhardt was supposedly born in 1793, but he is missing from the 1798 census. It is unclear if he was accidentally omitted, if the age listed was wrong, or if he was not in Grimm at the time of the census. Considering he would have only been 5 years of age and the youngest child, that seems unlikely but not impossible. It is also possible that he was one of the two youngest children in the 1798 census and his full name was either Friedrich Michael or Philipp Michael Engelhardt. The 1798 Grimm census is shown below for research purposes. The names of the two possible matches are bolded. Neither of those children is named in the 1834 Grimm census, although it's possible the married and moved to another village.
Head of the Household Philipp Andreas Engelhardt, age 61
Brother #1 Johann Martin Engelhardt, age 36 in 1816, deceased 1831
Wife of Brother #1 Anna Elisabeth Engelhardt, age 56
Child #1 Johann Friedrich Engelhardt, age 33
Wife of Child #1 Maria Barbara Engelhardt, age 29
Grandchild #1 Anna Katharina Engelhardt, age 8
Grandchild #2 Friedrich Engelhardt, age 4
Grandchild #3 Christian Jakob Engelhardt, age 1
Child #2 Johann Michael Engelhardt, age 24
Child #2 Johann Wilhelm Engelhardt, age 15
Child #2 Johann Jakob Engelhardt, age 13 years 6 months
Brother #2 Michael Engelhardt, age 41 [Missing from 1798 census, unless he was really Friedrich or Friedrich Michael Engelhardt, since his birth year, 1793, is within a year of the Friedrich Engelhardt born in 1792 and named in the 1798 Grimm census. 1857 census suggests his name may have been Philipp Michael.]
↑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 #145 in the 1798 census, Philipp Engelhardt family.
↑1834 Census of Grimm in the District of Saratov, Russia, Dated 2 February 1835, Revised Edition; Translated by Brent Mai, Concordia University, Portland, Oregon; Published by Dynasty Publishing, Beaverton, OR, USA; Copyright 2011; page 70, family #231, Philipp Andreas Engelhardt family.