In principle, I'd say not. It prohibits giving answers to the newer question.
If the other question is linked in the comments, that puts it in the "Linked" section. If more than this is deemed appropriate, perhaps a CW answer pointing to (the relevant part of) the answer to the other question can be posted.
In general, my condition for marking duplicate is:
Any answer to the old question will (mutatis mutandis) answer the new question.
This includes cases where the old question is more general; if OP doesn't understand the answers, they can edit to make this clear, and I'll support reopening (for the nature of the question will have changed to a follow-up question).
Of course, in specific cases I may deviate from the above as I deem fit.