龍鳳胎

龙凤胎
lóngfèngtāi
twins of mixed sex

CEDICT

boy-girl twins (Classifier: 對／对 m c)

Wiktionary

Entry Composition

1 龍鳳 lóngfèng dragon and phoenix
2 胎 tāi
  1. fetus
  2. classifier for litters (of puppies etc)
  3. padding (in clothing or bedding)
  4. womb carrying a fetus
  5. (fig.) origin
  6. source
  7. (loanword) tire