A 24-97 in The Immigration of German Colonists to Denmark and Their Subsequent Emigration to Russia in the Years 1759-1766.
B-280 in The Immigration of German Colonists to Denmark and Their Subsequent Emigration to Russia in the Years 1759-1766.
Rus 14-5 in The Immigration of German Colonists to Denmark and Their Subsequent Emigration to Russia in the Years 1759-1766.
Family #51 in the 1775 Grimm census.
Family #82 in the 1798 Grimm census.
Georg and his fiancee Anna Catharina Barbara Schmid immigrated to Denmark, departing from Altona, Duchy of Holstein, on 29 June 1761, and arriving in Schleswig, Duchy of Schleswig, on 05 July 1761.  They took their oath of allegiance on 24 July 1761.  In December of that same year the were recorded living at Number 4 Lueders Hof in Colony F13 Koenigsanbau, in the region of Flensburg. 
Note: The spelling of their surname is all over the place. The Grimm census records refer to them as Dumler or Tumler, eventually settling on Tumler in later census records. In The Immigration of German Colonists to Denmark and Their Subsequent Emigration to Russia in the Years 1759-1766, the name is also spelled Domler. German records show the name as Dumler. His father was Johann Philip Dumler.
The marriage date and place for Georg and Anna Catharina is not clear, but many couples married in towns just outside Denmark before they left Germany. Danish records say he was traveling with his fiancee,  so that suggests he and Anna Catharina were married in Denmark.
According to Danish records, the couple left Denmark by 24 April 1765.  Grimm was not settled until 1 July 1767.  If they arrived in Russia before the main wave of Germans to Russia in 1766, then they settled temporarily in another village, like Dobrinka, until Grimm was ready to be settled. For this reason, the birth place of their son Johann Georg is unclear. His birth year is estimated to be about 1766, but that could be off by a year in either direction. This means he could have been born one of these places:
Although most of the family remained in Grimm from 1775 through the early 1900s, they cannot be found in the first Grimm census, taken in 1767.  If they started out in a temporary village, they may not have officially relocated to Grimm until after August of 1767, when the first census was taken.
The first colony to be settled was Dobrinka in 1764. There is a good possibility their son was born there. But the Dumler family does not appear in the Dobrinka 1767 census. In fact, the Dumler name doesn't appear in Band 1, 3 or 4 of Einwanderung in das Wolgagebiet 1764-1767' by Igor Pleve.  These are the volumes which, combined, are loosely referred to as the first census of the Volga German villages, taken in 1767.
By 1775, however, the family was firmly settled in Grimm. By the time the census was taken, the couple had five children. Their oldest child, Ernst Friedrich, was born in 1763 in Koenigsanbau, Denmark.
1775 Grimm Census 
According to the 1775 census, his wife Anna Catharina was one year older than Georg, which makes her birth year 1729. She is probably: 
Gerabronn was about 120 miles from Leonbronn, Germany.
Georg is not listed in the 1798 census, nor is his wife.  He probably passed away and his son Georg took over the household. If his wife was still living, she probably remarried and lived with her new husband. A copy of the 1798 census entry for his family is shown below to connect him to his sons and their families. His youngest son, Martin, was born after the 1775 census and is not connected to his parents in any other official document.
1798 Grimm Census 
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