Rashi on Numbers 26:38/רש"י על במדבר כ״ו:ל״ח

1לאחירם OF AHIRAM — He is identical with Ehi (אחי) who went down to Egypt (Genesis 46:21), and because he was called after Joseph’s name (Sotah 36b), who was his (Benjamin’s) brother (אח) and greater, (רם) than he, he was also called Achiram.