The kinship sense (older woman / mother / sister-in-law term) is dialectal - mostly Wu and Min areas - and feels old-fashioned in standard Mandarin. Use 阿姨 for everyday 'auntie'.
culture
Far more common in modern usage: 阿姆 is the standard Chinese transliteration of American rapper Eminem (full name 埃米纳姆, but he's universally known as 阿姆 in Chinese hip-hop coverage).
