αδέρφια

Etymology: From ancient Greek ἀδελφός (adelphos) meaning 'brother', literally 'from the same womb' (a- 'same' + delphys 'womb'). The word shares the same root as Philadelphia ('city of brotherly love'). The plural form αδέρφια can refer to mixed-gender siblings or specifically brothers, while αδελφές refers specifically to sisters. This dual usage reflects the traditional grammatical pattern where masculine plurals can include mixed groups.