Sentence:  Francis Joseph ... had discovered that under the Constitution of 1867 he could exercise greater actual power over his dominions than his Prussian “brother,” at Potsdam or, in a merely personal sense, than his other pliable and <WSD>court-ridden</WSD> “brother” at the St. Petersburg Winter Palace. 
Meaning of the word marked with <WSD> tags:  Dominated or overly influenced by the (royal) court.