In the German Navy (both the Kaiserliche Marine and Kriegsmarine), the two ship names of Scharnhorst and Gneisenau were used together for sister ships; for example the SMS Scharnhorst and Gneisenau were sister armoured cruisers in WWI and the Germans also planned the names Ersatz Sharnhorst and Gneisenau for two never-built battlecruisers. The names also reappeared together in the Scharnhorst-class battleships of the Kriegsmarine in WWII. Why did the Germans keep on pairing these two ship names together?
Note: I do know that the namesake for these two ships were Prussian generals in the Napoleonic Wars, but why were the names used together on sister ships instead of other names of generals of the same era like Blücher?