Alexander faced pressure from his brother, Duke Constantine, to make peace with Napoleon. Given the victory he had just achieved, the French emperor offered the Russians relatively lenient terms–demanding that Russia join the Continental System, withdraw its forces from Wallachia and Moldavia, and hand over the Ionian Islands to France. By contrast, Napoleon dictated very harsh peace terms for Prussia, despite the ceaseless exhortations of Queen Louise. Wiping out half of Prussian territories from the map, Napoleon created a new kingdom of 1,100 square miles called Westphalia. He then appointed his young brother Jérôme as the new monarch of this kingdom. Prussia's humiliating treatment at Tilsit caused a deep and bitter antagonism which festered as the Napoleonic era progressed. Moreover, Alexander's pretensions at friendship with Napoleon led the latter to seriously misjudge the true intentions of his Russian counterpart, who would violate numerous provisions of the treaty in the next few years. Despite these problems, the Treaties of Tilsit at last gave Napoleon a respite from war and allowed him to return to France, which he had not seen in over 300 days.

What is the name of the Duke who pressured Alexander to make peace with Napoleon?