On February 4, 1783, Rapp married Christine Benzinger of Fiolzheim. The couple had two children, a son, Johannes (December 22, 1783 – 1812), and a daughter, Rosine (February 10, 1786 – 1849). Johannes, who trained as a surveyor, died at the age of twenty-nine in an industrial accident. Johannes's name is the only one listed on a stone in the Harmonist cemetery in Harmony, Pennsylvania. (The Harmonists did not mark their graves.) The marker was donated by non-Harmonists and the Society accepted it reluctantly. The specific location of Johannes's gravesite within the cemetery is unknown. Johannes's daughter, Gertrude (1808–89), later became a minor American celebrity and organized the Society's silk production at Economy, Pennsylvania. George Rapp later adopted Frederick Reichert (April 12, 1775 – June 24, 1834).