WordNet sense 1 ((astrology) a person who is born while the sun is in Gemini):

Gemini

WordNet sense 2 (a waterfall in the Snake River in southern Idaho):

Twin Falls

WordNet sense 3 (a duplicate copy):

counterpart, similitude

WordNet sense 4 (duplicate or match):

duplicate, parallel, duplicate

WordNet sense 5 (very similar):

siamese

WordNet sense 6 (being two identical):

matching, twinned

WordNet sense 7 (going well together; possessing harmonizing qualities):

matched

WordNet sense 8 (bring two objects, ideas, or people together):

couple, match, mate, pair, mate