Johann Conrad Leonhard, a son of Johannes Leonhard & Elisabetha Schäffer, was born 22 February 1729 and baptized on 25 February 1729 in the Evangelical Church of Sprendlingen, today a constituent part of the town of Dreieich, located about 10 kilometers south of Frankfurt am Main, in Hesse.
He married to Rahel Arnould, a daughter of Friedrich Arnould, on 29 July 1755 in the same church. They had four known children, each baptized in Sprendlingen: (1) Johann Friedrich, born 13 May 1756 and baptized 16 May 1756; (2) Conrad, born 19 October 1759 and baptized 21 October 1759; (3) Cyriack, born 8 February 1762 and baptized on 10 February 1762; and (4) Johann Philipp, born 18 December 1764, and baptized 21 December 1764.
Johann Conrad Leonhard and his family emigrated to Russia, departing from Lübeck by the ship Apollo with the skipper Detlov Merberg. On 29 August 1766 the family arrived at the port in Oranienbaum, Russia.
The Leonhards settled in Grimm about 1 July 1767. They are recorded there on the 1767 census in Household No. 80, along with the orphan Maria Katharina Schicketantz, a daughter of Johann Georg Schicketantz , who had been born on 29 June 1760 in Sprendlingen.
At the time of 1798 Grimm census, Philipp is recorded in Household No. Gm178 and son Jacob is in Household No. Gm179.
- Mai, Brent Alan. 1798 Census of the German Colonies along the Volga: Economy, Population, and Agriculture (Lincoln, NE: American Historical Society of Germans from Russia, 1999).
- Parish records of Sprendlingen (LDS Film No. 1193263).
- Pleve, Igor. Einwanderung in das Wolgagebiet, 1764-1767 Band 2 (Göttingen: Der Göttinger Arbeitskreis, 2001): 84.
- Pleve, Igor. Lists of Colonists to Russia in 1766: Reports by Ivan Kulberg (Saratov: Saratov State Technical University, 2010): 320.