Some oldest michael chu answer:
GDC 2017, about Ana Origins Photo
Michael chu: You’ve got your prime, original generation characters: Gabriel, Ana, Jack, Reinhardt, and Torbjörn. You have an 11-to-12 year old Pharah, you have McCree who’s just been recruited into Blackwatch, you have university-student Mercy who’s visiting the Overwatch base.”
17 ago 2016, official forums
User: The picture from Ana’s origin was said to be 20 years ago. She’s currently 37, so she joined Overwatch at the age of 17. By then Overwatch had recognized her ability as a renown surgeon and has a masters in Nanobiotechnology. How can that be possible?
Michael Chu: While Mercy is extremely intelligent and completed her education at a younger age (and in a shorter amount of time than usual), she definitely did not join Overwatch at age 17.
but I understand what you mean, it’s not a 5-2 year difference that should scare a possible relationship, Phamercy or Gency anyway.