Is “he should be seventeen” correct?

Question

Is the following sentence correct to describe a young man?

He should be seventeen.

My colleague was absolutely sure it was correct. I disagreed, so we had a bit of an argument. I would agree on either

He should be seventeen before he. . . .

or

He should be seventeen by now.

If the original sentence (“He should be seventeen.”) is actually correct, what makes it so?

Answer 1

It depends on the context. If someone asked you how old your third cousin is (whom, for example, you rarely see), you could respond with 'He should be seventeen'. Or, if a young lady asked you the appropriate age for a young man to date, you could respond the same. The way you're phrasing it, the statement sounds like a response to a question. You could desciribe someone this way, but it really is a vague description.