doubleton vs twosome

doubleton and twosome both are nouns.

Word	Noun	Adjective	Verb	Adverb
doubleton	Yes	No	No	No
twosome	Yes	No	No	No

As nouns, twosome is a hypernym of doubleton; that is, twosome is a word with a broader meaning than doubleton:

doubleton: (bridge) a pair of playing cards that are the only cards in their suit in the hand dealt to a player
twosome: two items of the same kind

Other hypernyms of doubleton include brace, couple, couplet, distich, duad, duet, duo, dyad, pair, span, twain, yoke.

doubleton (noun)	twosome (noun)
(bridge) a pair of playing cards that are the only cards in their suit in the hand dealt to a player	a pair who associate with one another
	two items of the same kind