What is another word for "twin"?

Roget's Thesaurus (1911) lists these synonyms for "twin": accessory, accompaniment, accompany, addition, adjunct, along, and, appendage, appurtenance, arm, associate, associated, association, attend, attendant, attribute, bear, biformity, binary, binate, binomial, biparous, biplicity, boat, body, both, brace, bracket, bring, cheek, coefficiency, coefficient, coexist, coexistence, colleague, collectively, comes, companion, companionship, company.