Arthur Fonzarelli, Better known as Fonzie or simply "The Fonz", was played by Henry Winkler for the full 11 year run of the show Happy Days.
Not much is known about Fonzie's family. He says in an episode that his father left when he was 12 years old. In the episode "The Cunningham Caper" he mentions that his mother used to sprinkle crushed asprin on his linguini when he wasn't feeling well. In another episode he also mentioned that when he needed his tonsils out, she lied and told him they were going to the parade, but he "broke her down" and got her to confess on the way to the hospital. He has a nephew named Raymond (Or Spike, as his friends call him) who appeared in the episode "Not with my sister, You don't!" in which he went on a date with Joanie Cunningham. He has a cousin named Chachi (played by Scott Baio) who dated and later married Joanie. In a later episode Fonie's half- brother, covieniently named Arthur (Artie), comes to see the Fonz to tell him their father died. His father left him a pocket watch, that incedentaly doesn't work.
Throughout the series, Fonzie is basically the sterotypical "cool guy" of the fifties. And while he works to maintain his reputation as the tough, high school dropout, he is also a loyal friend and devoted to the idea of family, but only those closest to him really get to see this side of him.
A notable example of this is in the 1974 episode "Kiss Me Sickly," in which Fonzie asks Richie to keep an eye on his girl for him while he goes away to help out with a demolition derby. When he returns home, Richie confesses that he had been taking Fonzie's girl up to inspiration point and made out with her. However, Fonzie doesn't want to hurt Richie since he had gotten with another girl at the derby, but he also wants to protect his reputation. While they are standing in his "office" (the men's bathroom at Arnold's) trying to decide what to do, someone walks in and hits Richie in the face with the door. They allow everyone to believe that the resulting bruise was caused by a hit from Fonzie, allowing his reputation and their friendship to both remain intact.