Harvey Kinkle, played in the 1996 movie by Tobias Mehler, then Nate Richert in the series, is a mortal boy whose full name is Harvey Dwight Kinkle.
As revealed in episode 62 (season 3), he has some Slavic ancestry. He was close friends with Sabrina Sawyer, Salem, Roxie King, Morgan Cavanaugh, Jenny Kelley, Valerie Birkhead and Brad Alcerro. Harvey is portrayed as a very popular and athletic young man, though not very bright. He is second string on the football team, and the object of affection of Libby Chessler, fueling Sabrina's rivalry with her. The character was first introduced in the comics in Archie's TV Laugh-Out #1 (December 1969).
Harvey was Sabrina's boyfriend until the 4th season, when he discovered that she was a witch in the season finale. The reason for this was that Sabrina had cast too many spells on him over the years and, when the limit was reached, his memory was no longer erased after each spell was reversed. After this, Harvey left the show.
Harvey made a few brief appearances during Season Five. In "Do You See What I See?", Harvey called Sabrina and apologized for the way he acted after learning she was a witch. Harvey returned to the show full-time in Season Six. Sabrina's Great Aunt Irma (played by Barbara Eden) later discovered Harvey knew Sabrina was a witch, and put him on trial to make sure he was trustworthy. Harvey was first attached to a lie detector which was not even plugged in, strapped to a spit and cooked, and even put on the torture rack, but he finally convinced Irma that Sabrina's secret was safe with him, and she let him go.
Harvey became Morgan's boyfriend for a time, but had developed feelings for Sabrina again, even coming to her rescue a couple of times. In season 7, it is revealed that Harvey is still in love with her. He makes Aaron Jacobs jealous since he is Sabrina's ex and they are still close. In "Spellmanian Slip", Harvey still has a special place in Sabrina's heart (with a room of his own). In "A Fish Tale", Harvey has also shown himself to be unselfish; when Aunt Irma turned Aaron into a goldfish, Sabrina tried unsuccessfully to reverse the spell, so she gave up her magic; Harvey harnessed Sabrina's magic, and changed Aaron back. When Sabrina talked to Aunt Irma, she found out that Harvey was able to undo her spell because he wanted to make Sabrina happy (which, in Irma's opinion was a more powerful motivation than Sabrina's, which was to defy Irma). Sabrina went to Harvey's apartment, only to find him gone; she found only a cardboard box with the vase that contained Sabrina's magic, a picture of them together, and a good luck note.
In the series finale, Sabrina realized that she and Harvey were soul mates, and she abandoned her wedding and rode off with him, her first and true love.