Johnny and Bobby Crawford on 'The Rifleman'

There weren't many kids on The Rifleman, other than child star Johnny Crawford, who played Lucas McCain's son, Mark. That helps make the appearance of Johnny's real-life brother Robert "Bobby" Crawford Jr. a little more memorable. Bobby appeared in three episodes, "Eight Hours to Die," "The Gaucho" and "The Second Witness," each time playing a different character. Shortly after his Rifleman cameos, Bobby would make a more lasting impression on TV viewers as Andy Sherman in the 1959 series Laramie.

Ron and Clint Howard on 'The Andy Griffith Show'

Ron Howard sits distinctly among the world's most famous child actors due to his early start as Opie on The Andy Griffith Show and starring run as Richie Cunningham on Happy Days. His brother Clint Howard also occasionally wandered Mayberry's streets quietly stealing scenes when he could. Clint appeared in five episodes as the mute toddler cowboy Leon, either offering a bite of his sandwich to main characters during chaotic scenes or simply appearing in the background as the world's most adorable wallflower.

Barry and Stanley Livingston on 'My Three Sons'

When Tim Considine (who played oldest son Mike Douglas) left My Three Sons in 1965, the show was down one son. Their solution? Have the Douglases adopt Ernie Thompson, the orphan pal of Chip Douglas. Most folks know that the actors who played Ernie and Chip were real-life brothers, Barry and Stanley Livingston, and of all the siblings on our list, they definitely shared the most episodes together: 236. We couldn't resist the opportunity to revisit the first episode where the brothers appeared together in 1963, "My Friend Ernie," pictured here.

Mike and Todd Lookinland on 'The Brady Bunch'

In the final season of The Brady Bunch, we got a glimpse of one of the Brady kids' real-life siblings in a rare episode that largely takes place outside the Brady household. While Mike Lookinland is beloved by TV history as Bobby Brady, his brother Todd Lookinland was also a child actor, with roles on shows like Gunsmoke, How the West Was Won, and, of course, that one time he joined his brother on set for The Brady Bunch episode "Kelly's Kids." In his starring episode, Todd, pictured here on the right, plays an adopted son to the Brady's friends Ken and Kathy Kelly. The episode, which was a failed backdoor pilot, follows as both Todd and his new parents adjust, allowing Todd to step into Mike's well-worn shoes as part of a new family.

Melissa and Jonathan Gilbert on 'Little House on the Prairie'

Speaking of adopted siblings, real-life adopted siblings Melissa and Jonathan Gilbert both appeared in the 1974 series Little House on the Prairie. Melissa was the show's star as Laura Ingalls and appeared in 205 episodes, but Jonathan's character Willie Oleson was introduced by the third episode, "Country Girls," and appeared in 180 episodes. The scene here is from "The Love of Johnny Johnson," the second episode the siblings appeared in together, which sees Melissa sparring with her TV sister Mary (Melissa Sue Anderson) for the affections of her crush. 

Image: Worldvision Enterprises CBS Television Distribution

Erin and John Moran on 'Happy Days'

In Happy Days' third season, actress Erin Moran (who played Joanie Cunningham) was 16, and her younger brother John was just nine. He appeared on the episode "Football Frolics" as Myron, which became his first acting role. The episode finds Richie, Potsie and Ralph babysitting 15 kids so they can make enough money to go to a football game. Myron gets assigned to Ralph, who groans at his new addition, while John's real sister Erin backs him up, standing right by his side.

Tracey and Jessie Gold on 'Growing Pains'

In its sixth season, Growing Pains saw its star Mike Seaver (Kirk Cameron) rapidly maturing for an episode called "Daddy Mike." The premise: Mike joins his pal Eddie at a meeting for single parents, where he meets a hot single mom. He pretends to be a single dad, and one of the kids recruited for the silliness that ensued was Jessie Gold, pictured on the left, the real-life sister of Mike's fictional TV sister, Tracey Gold. Jessie Gold appears as "Judith," in one of only four credited roles to her name. Meanwhile, Tracey went on to act in a ton of TV movies after Growing Pains.

Image: Warner Bros. Television Distribution

Candace and Kirk Cameron on 'Full House'

A much more well-known pair of TV siblings is the duo of Candace and Kirk Cameron, each stars of hit family sitcoms in their own right. Kirk landed his role first, though, starting his stint as Mike Seaver on Growing Pains in 1985. Candace started Full House in 1987. Their first encounter onscreen after that was in a 1988 episode of Full House called "Just One of the Guys." Kirk is cast as Cousin Steve, who pretty much ruins D.J.'s day when he arrives and has way more fun with Candace's TV dad, Bob Saget. The episode features the real-life siblings sharing a heart-to-heart in D.J.'s bedroom.

Image: Warner Bros. Television Distribution

Wil, Amy and Jeremy Wheaton on 'Star Trek: The Next Generation'

Wil Wheaton's role as Wesley Crusher on Star Trek: The Next Generation made him a hero to kids everywhere obsessed with the show. It makes you wonder if his actual siblings looked up to him just as much. Whether or not they did in their actual family home, in the first season episode "When the Bough Breaks," Amy and Jeremy joined their brother on set as two of the children stolen from the Enterprise by people suffering on an alien planet where there are no children. In the episode, Wesley saves the day, including his real-life siblings. You can pick them out in this photo, flanking another cast member family member, McKenzie Westmore, who was daughter to Star Trek make-up artist Michael Westmore.

Image: CBS Television Distribution

Fred and Ben Savage on 'The Wonder Years'

Another more established pair of TV sibling actors, Fred and Ben Savage each starred in shows that were massively popular in the 1990s. Fred's earlier hit, The Wonder Years, began in 1988, while Ben's hit, Boy Meets World, started in 1993. In between, Ben took a part in the 1990 Wonder Years episode "The St. Valentine's Day Massacre." In it, Fred plays the characteristically agitated Kevin Arnold, who recruits the help of a younger kid at school, Ben's Curtis Hartsell, to deliver a valentine to Winnie Cooper. Hilarity ensues when Curtis misses his mark and the valentine ends up with Becky Slater instead.

Image: The Black-Marlens Company New World Television