Complex sentence: Her sister Mary was the youngest daughter and also a member of Cumann na mBan while her brothers Hugh, Frank and Joseph became joined the Irish Republican Army and were members of a Flying Column during the War of Independence.
Split into simpler sentences: Her sister Mary was the youngest daughter and also a member of Cumann na mBan. Her brothers Hugh, Frank and Joseph joined the Irish Republican Army and were members of a Flying Column during the War of Independence.