N1
ともあろう
Of all people, Someone such as … (and yet)
有名な大学の教授ともあろう人が、ろくに敬語も使えないなんておかしい。
Of all people, it is strange that a professor of a famous university cannot even use keigo properly.
Explanation
「Nともあろう＋noun」 means 'someone as eminent as N, and yet ...'. The noun is a person of high standing, reputation or trust, such as a university professor, a prime minister, a famous doctor or a company head, and the speaker criticizes them for doing something that does not fit that position at all: 「有名大学の教授ともあろう人が、論文を剽窃するとは情けない」 (It's shameful that a professor at a famous university would plagiarize a paper). The noun after it is usually 「者」, 「人」, 「人物」 or 「組織」, in the form 「〜ともあろう者が」 or 「〜ともあろう人が」. It is full of shock and anger.
Mixed up with
「〜ともあろう者が」: after the fact; shock and blame that such a person did something absurd.
「〜たる者は」: before the fact; what a person in such a role should demand of themselves, e.g. 「リーダーたる者は、常に公平であるべきだ」 (A leader should always be fair).
「〜にして」: stresses that even a great person finds it hard, or that only this person could do it.