 Brentano was born in Offenbach am Main, the son of the Centre politician Otto von Brentano, a member of the 1919 Weimar National Assembly.The Brentano family, of Italian (Lombard) origin, had settled in the Landgraviate of Hesse-Darmstadt in the 17th century and were recognized as Hessian nobles, with close contact to important figures of the German Romanticism, including Goethe, Savigny and Arnim.He was related to famous German poets such as Clemens Brentano (1778–1842) and Bettina von Arnim (1785–1859).