姉妹
しまい · shimai · JLPT N3 · noun
sister
👭 姉妹 = older sister (姉) + younger sister (妹)
Both kanji carry the woman radical 女. 姉 (shi) is the older sister and 妹 (mai) the younger, so the word lists them in age order: shi + mai = sisters. The same pattern gives 兄弟 (kyoudai), older + younger brother.