The children of late singer Michael Jackson, Prince Michael Jackson II (Blanket), Prince Michael Joseph Jackson Jr. and Paris-Michael Katherine Jackson (L-R) stand on stage during the "Michael Forever" tribute concert, which honours late pop icon Michael Jackson, at the Millennium Stadium in Cardiff, Wales October 8, 2011.[Photo/Agencies]

Tens of thousands of fans rocked to the hits of Michael Jackson on Saturday at a tribute concert his brothers hoped would put the spotlight on his musical legacy after so much controversy.

The late singer's children -- Prince, 14, Paris, 13 and "Blanket," 9 -- appeared on stage briefly to address the crowd and at the end joined other family members dancing to "Don't Stop 'Til You Get Enough."

"We're very happy to be here on this special night to honor our father," said Paris, dressed in a red jacket similar to the one worn by Jackson in his groundbreaking "Thriller" music video.

The "Beat It" star, one of the most successful yet troubled artists of the pop era, died in 2009 aged 50 while rehearsing for a series of comeback concerts.

The "Michael Forever" tribute in Cardiff, Wales, coincides with the involuntary manslaughter trial of the singer's doctor in Los Angeles, drawing criticism from some fans and members of his family.

Brothers Jermaine and Randy boycotted the event because of the timing, while sister Janet said it would be too painful to perform in Cardiff during the trial.

But it had the blessing of his mother Katherine, who was at the gig, and Michael's older brother Marlon said it should be seen as a celebration of Jackson's music.

"They (the fans) have the right to (protest)," he said backstage. "I think they have the right to do whatever they feel, but we're celebrating the positive side of our brother's life.

"We know our brother better than anybody else and he would love that we are doing this for him and remembering him in that way."

"MICHAEL SUFFERED"

U.S. musician Ne-Yo kicked off the four-hour extravaganza at the Millennium Stadium with the tight beats of "Billie Jean" before slowing the tempo in "The Lady In My Life."

"It's not about the controversy, it's not about the trial, it's not about his death. It's about celebrating his life, it's about celebrating his music," Ne-Yo said from a stage shaped like a giant glove.

British boy band JLS sang "The Way You Make Me Feel" before being joined by three of the original Jackson 5 -- Marlon, Tito and Jackie -- in a rendition of "Blame it on the Boogie."

"Can you feel his spirit in the room tonight?" called out Marlon, and the mostly young crowd screamed "Yes!"

Jackson's sister La Toya performed live in public for the first time in nearly 20 years, while three of his nephews appeared in their band 3T.

"I had absolutely no intention of performing," La Toya told Reuters. "I was hesitant about this and at the last minute I said you have to do it for him ... and I did, so I'm happy that I did. It's worth honouring him this way."

The lineup also featured Christina Aguilera, Cee Lo Green, Beyonce on video and Jamie Foxx, and among British stars appearing were Leona Lewis and Diversity.

Toward the end, pictures of Jackson were beamed on to giant screens as "empress of soul" Gladys Knight, accompanied by a gospel choir, sang "Gone Too Soon."

Earlier, her powerful rendition of "Believe in Yourself" was a highlight, and she was joined in a duet of "I Just Can't Stop Loving You" by Motown great Smokey Robinson.

Robinson told Reuters: "There will be many mimics, but there will never be another Michael Jackson.

"He got to the point where he had no private life whatsoever," he added.

"When you are in a business that you love and you are doing what you love, however you can't go out and just get in your car or go to the store or go to the movies -- that's got to be rough. That's what he suffered."

Reaction was mixed among people streaming out of the arena after the gig, with many ecstatic but some underwhelmed by "under-rehearsed" numbers and long gaps between some songs.