형제자매=兄弟姐妹 (older brother, younger brother, older sister, younger sister).
wrong, the third character is 姉 not 姐, don't mix in Chinese character with Korean hanja
Indeed, it's 兄弟姊妹, which also exists in Chinese, actually.
姊 is the canonical form of 姉.
From '姉': 네이버 한자사전: