Coeval
Of the same or equal age or duration.
For example, the two elderly men were coeval with one another.
Coeval usually refers to coexistence for a very long time.
'Coeval' comes from the Latin 'coaevus' meaning 'of the same age.' 'Coaevus' is derived from the prefix 'co-'('in or to the same degree') and 'aevum' ('age' or 'lifetime').
The root 'ev' comes from 'aevum' as in 'longevity.'