Both Harry and Voldemort are half blood's.

Both Harry Potter and Lord Voldemort are half-bloods. Harry is half-blood because his mother was Muggle-born (Lily) and his father was pure-blood (James). Voldemort is half-blood because his father was a Muggle (Tom Riddle Sr.) and his mother was a witch (Merope Gaunt). This shared heritage is thematically significant throughout the series.