First you would need to determine the "country or nation" which bestowed the title. Most have records of such, but there are usually separate organizations and registers for each nationality.

Second, if his title was "Sir" he may have been a "knight" in the United Kingdom. Knighthood is not hereditary and is those honored as such are not considered "nobility." Nobles are those will titles such as Duke, Marquess, Earl, Viscount, or Baron (or the corresponding female equivelant).

Some Nobles are also knights, but the two do not have to go together. Some knights later become nobles, being further honored by the Monarchy with a peerage; however then they tend to assume the style of name that corresponds with their addiional title; such as Lord.

If he was a Knight, the "order" will help you find a list. Initials following the name ussually stand for the particular "Order of Knighthood" to which he belonged; for example, K.C.B. is for the Order of Bath; K.B.E. = Order of the British Empire; or occasionally some are knighted without membership in a particular order and the letters Kt. stand for Knight Bachelor