There is no "right or wrong" here, it's a matter of accent or dialect. In most of the United States (outside of New England and parts of the New
York City and New Jersey area), the pronunciation of American English has lost the "a" sound that is found in the word "cat" before "r", and so all the words which would have that sound in England, Australia, or Boston, Massachusetts, end up sounding like they contained the word "air". So to most Americans,
Aaron and
Erin are pronounced the same, as are the pairs Kerry/Carrie, Berry/Barry, fairy/ferry, Harry/hairy, Mary/merry, Perry/parry, and Terry/tarry. Most people in England and Australia would never think of these pairs as having the same pronunciation, but outside of the Northeast the huge majority of Americans would think that they are identical.