Married (1764) to Johanna Schartow. Boswell tells us that he "has a little office that enables him to live genteelly".
Boswell stayed with the adopted family of Stielow's fiance, Johanna Schartow, in Berlin in 1764. The wedding ceremony was performed at the house of the Kircheisen's on July 18, 1764, and was attended by Boswell. In the evening the company all went to Stielow's house where "we had a collation and good wine. We laughed much and many a joke went round. [...] We put the bridegroom and bride to bed in night-gowns.". Boswell concluded that it had been "one day of sure satisfaction".