Schloss Steinau has housed a Brothers Grimm memorial with exhibits from the collections of the Staatliche Schlösser und Gärten Hessen since 1985. These come primarily from the estate of Marko Plock, a descendant of Wilhelm Grimm. When the furniture, sculptures and tapestries from the Löwenburg in Kassel, which had been presented here in the meantime, returned to their original place in 2015, the rooms that had become vacant were used to enlarge the previous exhibition. In autumn 2014, after the closure of the Brothers Grimm Museum Kassel (Palais Bellevue - Schöne Aussicht 2), which had been in existence since 1959, parts of the holdings came to Schloss Steinau and were brought together with the objects already there. The newly designed permanent exhibition was opened in August 2015.

The half-timbered Renaissance building with a stone base was the home and official residence for the bailiff of the Counts of Hanau. The bailiff Philipp Wilhelm Grimm lived here with his family from 1791 to 1796; his eldest sons, the later linguists and fairy tale collectors Jacob and Wilhelm Grimm also lived here. The building later served as a district court in 1975. Since 1998, it has housed the Brüder Grimm-Haus Steinau museum, which was once again redesigned in 2011. The Brothers Grimm are the focus of the museum, but their ancestors and descendants are also brought into view. The artistic work of Ludwig Emil Grimm is another focus. Throughout the museum, modern exhibition technology, audiovisual units and media stations are used.