Question: Princess Frederica Dorothea "Louise" Philippine of Prussia, was a member of the House of Hohenzollern, and was a niece of which King of Prussia from 1740 until 1786, the longest reign of any Hohenzollern king?
Sentence (from "List of monarchs of Prussia"): While still nominally two different territories, Prussia under the suzerainty of Poland and Brandenburg under the suzerainty of the Holy Roman Empire, the two states are known together historiographically as Brandenburg-Prussia.
Relevant evidence: No