~の(中の)一人 (one of)

The partitive pattern [group/phrase]の(中の)一人, literally 'one person of [group],' used to identify someone as a member of a group. グループの中の一人 ('one of the group'), 三人の中の一人 ('one of the three'), 最も優れた画家の一人 ('one of the most outstanding painters'). The 中 emphasizes 'among many'; both ~の一人 and ~の中の一人 are standard renditions of English 'one of the X.'