Thomas Braun's paternal grandfather Felix Friedmann-Braun (1861-1934) was the son of Samuel Friedmann (1823-1896) and Marie Agnes Friedmann née Braun (1835-1906), with ancestors of the Fränkel family dating back to 16th century Vienna. More recent relatives on this side of the family are Felix Friedmann-Braun's siblings, Hedwig Schneider née Friedmann (1860-1932), Arthur Friedmann (1865-1935), Vally Friedmann (1868-1932), Friedrich Franz Friedmann (1876-1953), and Ilse Rosenthal-Schneider (1891-1900), his niece.

Thomas Braun's paternal grandmother Gertrud Friedmann-Braun née Lehfeldt (1870-1942) was the daughter of Leonhard Lehfeldt (1834-1876) and Therese Lehfeldt née Lehmann (1835-1925), linking them to the extensive Lehmann-Lehfeldt family of the Berlin and the Lower Silesia Glogau (Głogów) area, with Veit and Jacoby ancestors dating back to 16th century Prague. More recent relatives of this side of the family include Leonhard Lehfeldt's siblings Paul Lehfeldt (1848-1900), and Clara Lehfeldt (1846-1907), who married the painter Paul Meyerheim (1842-1915). Leonhard Lehfeldt's father, Joseph Lehfeldt (1804-1858), was a publisher, and so were Therese Lehfeldt's father Joseph Lehmann (1801-1873), editor of the literary journal 'Magazin für die Literatur des Auslandes', and her brother Felix Lehmann (1851-1914), closely linking the family to the publishing and literary scene, and the artists and intellectuals of Berlin.