Rupert IV, Count of Nassau

[1] Rupert is mentioned for the first time in a charter dated 20 March 1198, together with his mother and his brother Henry II.

[3][4] The Nassau possessions in this area were expanded around 1214 when Rupert's brother Henry received the Imperial Vogtship (Reichsvogtei) over Wiesbaden and the surrounding Königssondergau, which he held as fiefdoms.

[5] About the year 1200, Rupert, together with his brother Henry, began building Sonnenberg Castle on a spur of Spitzkippel peak in the Taunus above Wiesbaden.

This was intended for protection against the Archbishop of Mainz and its vassals, the Lords of Eppstein, who held the lands bordering Wiesbaden.

To settle the dispute, Nassau paid 30 Marks to the cathedral chapter in 1221 to acquire the land of Sonnenberg Castle.