Calling them “The Carpenters”—with the capitalized definite article “The”—is the appropriate and grammatically correct way, in much the same way that place name “The Netherlands” formally requires the capitalized “The.” The presumption in the use of such capitalized appellations as “The Carpenters” is that the performers for which the name stands have the same family names (or, if they have different surnames, belong to the same family), and have decided to use the appellation as a brand or trademark. In the case of such place names as “The Netherlands,” the use of the capitalized definite article “The” and the proper name in plural is meant to indicate a collection of islands, mountains, or other geographic features. The capitalization of the “The” is a just matter of choice and style, though; in the case of “the Philippines,” for instance, the official style doesn’t require capitalizing the “the.”
