Denethor - The third branch of Elves, which played only a minor role in the First Age were the Nandor (their descendants would play a greater role in the Third Age).  The first leader of the Nandor was Lenwë.  The Elves who would become the Nandor began the Great Journey with Oromë, but stopped east of the Misty Mountains and settled there.  Many years later, a group of Nandor, under Lenwë's son Denethor, entered Beleriand and were reunited with their Sindarin brethren.

"Then one arose in the host of Olwë, which was ever the hindmost on the road; Lenwë he was called.  He forsook the westward march, and led away a numerous people, southwards down the great river (Anduin) and they passed out of knowledge of their kin until long years were past.  Those were the Nandor; and they became a people apart, unlike their kin, save that they loved water, and dwelt most besides falls and running streams.  Greater knowledge they had of living things, tree and herb, bird and beast, than all other Elves.  In after years Denethor, son of Lenwë, turned again west at last, and led a part of that people over the mountains into Beleriand ere the rising of the Moon." ~The Silmarillion, chap. 3 (Of the coming of the Elves)