Marvel was pretty definitive this week about Peter Parker. They placed the spider-bite at thirteen years ago, and he's said many times that he was 15 when he started being Spider-Man. Simple arithmetic works the same in the MU, so there you have it.
The relevance to Cyclops being that it remains the case that Cyclops and the O5 had their first mission against Magneto at Cape Citadel some time after Parker debuted as Spider-Man, and Scott was ~16-17 at the time.
Emma I always figured as being somewhat older, for a lot of the reasons others have cited, and having her be the same age or younger than Scott seems like a bit of a retcon and/or her straight out lying about her age. But Scott is 28-29, 30 on the outside, and can never be much older than that lest it become clear that Peter Parker must likewise have finished out his third decade.