Osmond Family Concert Live On GMA

America's first family of music performed live on "Good Morning America" this morning to celebrate their 50th anniversary in showbiz.

The nine Osmond singing siblings — Donny, Marie, Alan, Wayne, Merrill, Jay, Jimmy, Viril and Tom – were joined by their 150-member extended family onstage at Walt Disney World after performing their hits "We're Having a Party" and "He Ain't Heavy, He's My Brother."

What started as a Las Vegas anniversary concert has now turned into a worldwide tour, PBS special and charity campaign to raise awareness for the Children's Miracle Network.

It was the first time the all siblings appeared together on stage in more than 27 years. They enjoyed it so much, that now Donny and Marie are planning to perform together again in Las Vegas when the tour is done.

"We're going to work together after 20 years … pray for me," joked Marie on GMA.

"She keeps making fun of me that I can't dance as well as she can…" Donny replied, referring to Marie's recent appearances on "Dancing With The Stars."

The Osmonds say Disney World is the appropriate place for their 50th, since they credit Walt Disney himself for discovering them.

The tour also marks the 25th anniversary of the Children's Miracle Network, which the Osmond siblings helped establish with their parents to raise funds for children's hospitals around the country.

"We are very grateful for the legacy our parents left us … we inherited their hearts … we have aligned with 170 of the premier hospitals across the nation … this year is huge because we're launching it worldwide," said Marie.

Click here to learn more about the Children's Miracle Network.

Click here to learn more about Osmond 50th Anniversary PBS special, which will be available on DVD and CD on April 1.