His father was Karl-August Thomae, the rector of a school in Laucha, and his mother was Emilie Gutsmuths. Carl Johannes was the eldest of his parents two children and was not expected to survive to adulthood.
Kanyang ama ay Karl-August Thomae, ang rektor ng isang paaralan sa Laucha, at ang kanyang ina ay Emilie Gutsmuths. Carl Johannes ay ang pinakamatanda ng kanyang mga magulang at dalawang bata ay hindi inaasahan na makalibre sa adulthood.