Tens of thousands of fans rocked on Saturday to Michael Jackson hits at a tribute concert his brothers hoped would shed a positive light on the late King of Pop after so much controversy.

U.S. singer Ne-Yo kicked off the four-hour Jackson extravaganza at the Millennium Stadium in Cardiff 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 in the shape of 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 rousing 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!

The gig has been beset by problems ranging from rebelling fans to unsold tickets and a headline act pulling out at the last minute.

But Michael's older brother Marlon wanted the tribute attended by Jackson's mother and three children to be remembered for different reasons.

They (the fans) have the right to (protest), he said backstage ahead of the Michael Forever concert. I think they have the right to 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.

The Thriller singer, 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.

FAMILY, FANS DIVIDED

Some fan clubs questioned where the money made from the concert was going and complained about it being held at the same time as the involuntary manslaughter trial of Jackson's doctor in Los Angeles.

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

But another sister La Toya was set to perform live in public for the first time in nearly 20 years.

In addition to the Jacksons, the lineup includes Christina Aguilera, Cee Lo Green, Jamie Foxx, Gladys Knight and Smokey Robinson, and among British stars appearing will be Leona Lewis, Alexandra Burke and Diversity.

Black Eyed Peas, originally confirmed to attend, pulled out earlier this week without explanation.

While acknowledging that the difficulties had taken some of the gloss off the event, fans at the stadium were excited to be able to pay homage to their idol.

He was the best there is, said Kerry Hall-Smith, from Cardiff, who had a special T-shirt printed for the event.

He's one of the legends, he's like Elvis. They are the people you remember forever.