Twin 
Verb
Noun
pair, couple
Emma twinned her skirt with a blouse in a similar shade of blue
Identical twin
Matthew and Mark are twins; it's almost impossible to tell them apart, unless you know them really well
Adjective
Identical
Jane bought twin candlesticks, one to go at either end of the table
Synonyms
Adjective
Noun
person who looks like another
double
clone
copy
doppelganger
one half of a pair
match
mate
equivalent
half
identical
Double
matching
dual
duplicate
the same
dual
Duplex
Antonyms
Single
Individual
Separate