I think
Aaron is one of those names that people pronounce either AAA-ren or EIR-en and the bearer of the name just goes with the flow. It's not really a different pronunciation. It's a different accent. Like HAA-ree vs HAIR-ee. My name is also an example. Some people pronounce it so that the first syllable rhymes with "can" and others pronounce the first syllable with a flatter A sound. Actually, my father pronounced it with a flatter A sound, while the rest of my family did not. This isn't something you say, "No no no, it's EIR-en, not AAA-ren" about.