While twins emerging as top actors in Hollywood is fairly unusual, they may not be as rare as you think. Many directors and producers like to go with twins when they have to fill roles for children. When a young actor has an identical twin, they don't have to upset shooting schedules due to illness, doctor's appointments and fits of pique. The twins may be able to alternate shooting responsibilities and share the workload. Twins can also emerge as adult actors. Here are five sets of twins you have seen on screen.

Tia Mowry and Tamera Mowry-Housley


The Mowry sisters became stars on the series "Sister, Sister," which was a staple of children's programming from 1994 through 1999 and is still seen frequently in syndication. "Sister, Sister" is about two twins who get separated at birth but find each other again in their teenage years and learn about each other's differences and similarities. Tia Mowry has gone on to star in "Seventen, Again" and "The Game." Tamera Mowry has starred in "The Hot Chick." While neither sister appear to be candidates for the Oscar or Emmy, both are extremely likable and have been quite popular.

James Phelps and Oliver Phelps


The Phelps brothers play Fred and George Weasly in the entire "Harry Potter" series. Fred (James) and George (Oliver) are Ron Weasly's brothers and they are two of the biggest pranksters and tricksters at Hogwarts Academy. Both brothers have appeared in eight of the Harry Potter movies and both of their voices have been used on the Harry Potter video games. While they appear quite a bit older than their on-screen characters are supposed to be, that hasn't diminished fans enjoyment of their hilarious work!

Mary-Kate and Ashley Olsen



These two megastars began their acting careers when they were chosen to perform the role of super-cute toddler Michelle Tanner on the 1987 television hit "Full House." They were clearly adorable children and the fact that both could get of funny one-liners helped ensure the show's success. The two went on to star in a series of their own made-for-kids videos that were incredibly profitable for the twins. They have also become fashion designers and sell a weird but popular line of young women's fashions.

Cole and Dylan Sprouse


These twins first made it to the small screen when they shared the role of Patrick Kelly on the hit show "Grace Under Fire" starring Brett Butler from 1993 through 1998. Both showed great timing with their jokes and one-liners and that helped the show have a successful run. However, their most famous role was as Julian in Adam Sandler's hit movie "Big Daddy." With Sandler in the role of Sonny Koufax, Julian learned how to curse like a long shoreman, eat junk all day and urinate without benefit of a toilet. All valuable lessons for any youngster.

Joel and Benji Madden


These two musicians from "Good Charlotte" and they were seen frequently on the small screen when the twins dated Nicole Richie and Paris Hilton. After the socialite girls' friendship ended, so did many of the TV appearances of Joel and Benji. However, their high-profile musical stardom has kept them in the public spotlight for years, and it's likely that you'll see them at any number of musical awards shows!