Peregrin Took - The Thain was the traditional military leader of the Hobbits of the Shire.  The Hobbits first chose a Thain to rule them when Arvedui, last King of Arnor, died.  Over time the Thain became a hereditary position, originally held by the Oldbuck Clan. Since 740 SR, the Thainship has remained within the powerful Took clan. Since the Thain ruled in the place of the King, in principle his office was equal to the Ruling Steward of Gondor, albeit in power over a much smaller area. (http://en.wikipedia.org/wiki/Thain)

Boromir - Steward was the traditional title of a chief counsellor to one of the Kings of Gondor. During the time of the Steward Pelendur, from the famous House of Húrin, this title became hereditary, passing the station of counsellor from father to son, much like the Kingship.  After the death of King Eärnur, who left no heir to the throne of Gondor, the Steward Mardil Voronwë became the first of the Ruling Stewards.  The Stewards watched over the throne until it could be reclaimed by a true King of Gondor, an heir of Elendil.  (http://en.wikipedia.org/wiki/Steward_of_Gondor)