Theobald married Louisa Elizabeth Heames, daughter of prominent Detroit civil engineer Henry Heames, in Detroit on March 27, 1879, and had five children between 1880 and 1892.
Theobald menikahi Louisa Elizabeth Heames, putri teknisi sipil Detroit terkenal Henry Heames, di Detroit pada 27 Maret 1879, dan memiliki 5 anak antara 1880 dan 1892.