- His son, Carl Apollo, was the 3rd of 8 sons.
He studied theology in Marburg. He became pastor in Arfeld Mar. 1, 1789. He was later a school inspector on one-half of Kreis Wittgenstein from 1809 to 1834.
He was the son of several generations of Evangelical Lutheran pastors (back to his Grandfather, Johannes Georg Groos b. 1696). By the time of Johannes, the Reformation was well entrenched in Wittgenstein, which is in the western side of present-day Germany, near the Rhine and Cologne. Erndtebruck, where the Martin family is from, is located the same small region (now called Siegen-Wittgenstein, in the south-east corner of North Rhine/Westphalia).
Also see: The German Connection, volume 23 No. 2, Second Quarter 1999, pp. 45-46.
Also see: Frederick Charles Chabot, With the makers of San Antonio: Genealogies of the early Latin, Anglo-American, and German families with occasional biographies (1937, republished later). This has a section on the Groos family and descendants on about 379-81.