This is a double portrait of two brothers, Ferdinand (1721-92) and Charles (1713-80), Dukes of Brunswick-Wolfenbüttel. Ferdinand is on the left, holding a marshal's baton and wearing the uniform of the Old Brunswick Regiment (No. 5) in the Prussian army, the star and ribbon of the Order of the Garter and the cross of Bauer-Brandenburg. Charles is on the right, wearing the same uniform and the star and orange ribbon of the Order of the Black Eagle. Charles succeeded his father as Duke of Brunswick-Wolfenbüttel in 1735. Ferdinand commanded the British and Hanoverian armies at the Battle of Minden and was a distinguished allied general in the Seven Years' War. He received the Order of the Garter in 1759.

In 1767, shortly after his sister Augusta married Charles William Ferdinand, Duke of Brunswick-Wolfenbüttel, George III bought 'twenty or more Miniature or colour'd drawings copied from the German of the House of Brunswick' and this miniature was among them. Charles' head is a copy of a portrait by Johann Georg Ziesenis. Ziesenis painted Ferdinand in a similar pose to the one here, which may be the basis for this miniature, but Ferdinand also had his portrait painted in England around 1759 by Robert Edge Pine. The identity of the artist is unknown.