ともあろう

The expression ともあろう is used to express surprise, disappointment, or criticism that someone of a certain high status, reputation, or position has done something unworthy of or unbefitting that status. It carries the nuance of "someone who should know better" or "of all people, someone like…"

It is typically attached to a noun representing a person or entity of high standing – a professional title, respected role, or prestigious organization – followed by a phrase describing behavior that is considered inappropriate or surprising for that status.

Structure

Noun + ともあろう + 人/者 + が

The noun before ともあろう identifies the status or role, and the phrase after it describes the unexpected or unbecoming action. The words ひと人 or もの者 (もの) often follow ともあろう, and the subject-marking particle が frequently appears to emphasize the subject.

Nuance

This grammar point always carries a tone of reproach or disbelief. The speaker feels that the person's actions fall short of what is expected given their position. It is a formal and literary expression, most commonly found in written Japanese, news commentary, or serious spoken contexts.

Important notes

• ともあろう is almost always used in negative evaluations – you wouldn't use it to praise someone.
• It is often followed by expressions of disbelief or criticism such as とは、なんて、 べきではない、or しんじられない信じられない.
• The noun before ともあろう must refer to something with recognized prestige or authority. It would sound unnatural with ordinary or low-status nouns.