twinner

noun3

1. •
   One who visits or interacts with a sister city of their own city.

   • Beyond correspondence, twinners around the country got very interested in elaborating their relation to their paired city by visiting it. — 1993
2. •
   One who is identical, is similar, or is a counterpart, to another person.

   • The twinner of Jack's ailing mother, a faded movie actress named Lily Cavanaugh (who was billed in her time as the “Queen of the B Movies”), […] — 2016
3. •
   One who gives birth to twins; a breeder of twins.

   • Ewes yeerly by twinning rich maisters doo make, the lamb of such twinners for breeders go take — 1557