Complex sentence: In German he is known "Richard Fürst zu Sayn-Wittgenstein-Berleburg" since titles of nobility, including "prince", have not been legally recognized under German law since 1919.
Split into simpler sentences: In German he is known "Richard Fürst zu Sayn-Wittgenstein-Berleburg". Despite the nomenclature, Herr Konstantin is not actually a "prince" under German law since titles have not been recognized under German law since 1919.