Oliver Rivers was a student in Harry’s year at Hogwarts (HPM, Pm).
Oliver Rivers was one of the original forty students at Hogwarts that J.K. Rowling created. He never appeared in canon, but did appear in the BBC interview with J.K. Rowling in 2001, "Harry Potter and Me." His name also appears in a new writing from J.K. Rowling on Pottermore, The Original Forty. (HPM) (Pm)
From the Web
This source provides a good analysis of what happened to the original forty.