Complex sentence: "Kawatare" (彼は誰) literally means "Who is he/she?"; "kataware" also has the same sound as a word meaning one of the couple (片割れ).
Split into simpler sentences: Kawatare (彼は誰) literally meaning "Who is he/she?". "Kataware" also has the same sound as a word meaning one of the couple (片割れ).