It's not an overtly feminine sounding name so I can see it on a boy, but, country's are usually personified as feminine though, which makes me think it should really stay as a feminine name.
I pronounce
Aaron - Ar-in not Er-in so it wasn't immediately apparent to me as a variant spelling. If his parents did mean it like this I agree they should have stuck with the spelling
Aaron, but If they were wanting to honour irish heritage or something then that's not so bad.