Hanna B. answered 04/30/19
Native Korean Tutor / Culture Ambassador :)
Answer: 연세가 있으시다.
This would be a proper way for saying someone is old in the politest way. 연세 simply is a 존칭 (polite language to someone older than you) for 나이 (age). And notice that I said 있으시다 (polite language for 'has') instead of 있다 (has).
FYI) 연세 is commonly used someone over age 40-50 ish.
So you would say,
A: 그사람 우리 또래야?
(Is that person our age?)
B: 아니, 그분 연세가 있으셔.
(No, he/she is older)