In the UK, the most usual pronunciation of ‘Aaron‘ is /ˈɛːɹən/ and of ‘Erin‘ /ˈɛɹɪn/. That means that ‘Aaron‘ starts with the same vowel as most of us use in ‘air’ and ‘Erin‘ with the same vowel most of us use in ‘egg’.
David Nilsen is the former editor of Fourth & Sycamore. He is a member of the National Book Critics Circle. You can find more of his writing on his website at davidnilsenwriter.com and follow him on Twitter as @NilsenDavid.