noun
Siamese twins; conjoined twins
Medical and general term for twins physically joined at birth. The term 'Siamese twins' is historically derived from Chang and Eng Bunker, but 'conjoined twins' is now preferred in medical contexts.
シャム双生児は、体の一部が結合した状態で生まれる双子のことです。
Siamese twins are twins born with parts of their bodies joined together.
More formal medical term for conjoined twins, literally 'joined twins'. シャム双生児 is the common lay term.
From English 'Siamese twins', referring to the famous conjoined twins Chang and Eng Bunker from Siam (now Thailand). The term entered Japanese as a loanword with the kanji 双生児 (twins).