Childhood and family... I am Black

As revealed in "Zoo or False," Barney was born 7 years after the first man landed on the Moon, thus making 1976 his year of birth. He was raised in Port Richmond, Staten Island by his mother Loretta (younger version voiced by Megan Mullally, played by Frances Conroy), who was apparently very promiscuous. His father proved to be an ongoing mystery in the series. When Barney was young, he asked his mother who his father was, and as The Price is Right happened to be on TV at the time, she pointed to Bob Barker and replied "Oh, I don't know. That guy." Barney believed the lie wholeheartedly, and years later confronted Barker in the season 2 episode "Showdown" with the intention of naming Barker as his father on national television, until he panicked at the last minute and could not go through with it. As a child, Barney was terrible at sports, and from various episodes it is shown he had few friends (one scene shows that no one attended his birthday party). In the episode "The Leap," Lily reveals that Barney planned on being a violinist when he was young.

In "Natural History", it is mentioned that a man named Jerome Whittaker, who up to then Barney believed to be his uncle, signed a form claiming to be Barney's father. Barney finally met Jerome (John Lithgow) again in the episode "Legendaddy" and learned that he is in fact his father. Upon meeting, Jerome felt forced to act in the same confident, womanizing manner as Barney in order to impress him, and also because Barney seemingly refused to see him any other way. Barney eventually broke down and accused Jerome of walking out on him (Barney's mother forbade Jerome from seeing Barney due to his drug use and wild lifestyle). Jerome, who could offer no excuse, apologized and pleaded with Barney to allow him to be a part of his life, which Barney was open to, but apparently not ready for yet. Later in the sixth season, in "Hopeless", Jerome tries to impress Barney by acting like his old self, but later reveals he was just pretending. Barney, nevertheless, willingly listens to advice from Jerome about settling down in his older days.

Barney has three half-siblings: James (played by Wayne Brady), from his mother's side, a gay African American who is getting a divorce and has with an adopted son and daughter (as revealed in the season seven episode "The Rebound Girl"); Carly (played by Ashley Benson), a university student from his father's side with whom Ted hooks up, on Barney's insistence in "Ring Up!", and Jerome Jr. (JJ), from his father's side, who is 11. He also has a female cousin named Leslie, as seen in the episode "Okay Awesome".