LOS ANGELES (AP) — The Jackson family is determined to move on in order to protect Michael Jackson’s legacy and make sure his three children are well, family friend Al Sharpton said Tuesday.

“They’ve had challenges before,” Sharpton said on ABC’s “Good Morning America.” “They always rallied.”

Jackson’s parents wasted little time demanding authority over their son’s financially strained empire and guardianship of their fatherless grandchildren. The big question is who, if anyone, will contest them?

Early Monday — just four days after the death of the King of Pop — lawyers for Katherine and Joe Jackson won temporary custody of Michael Jackson’s three children and moved to become administrators of his estate.

Judge Mitchell Beckloff granted 79-year-old Katherine Jackson temporary guardianship of the children, who range in age from 7 to 12. He also gave her control over some of her son’s personal property that is now in the hands of an unnamed third party. But the judge did not immediately rule on her requests to take charge of the children’s and Jackson’s estates.

The swiftness of the legal motions underscore the fact that Jackson’s death leaves a vacuum if he died without a valid will. If no will is filed, the number of potential claimants that could emerge seeking custody of the children or a piece of his empire are many.

Jackson’s parents claimed in documents filed in Superior Court on Monday that there is no will. A person with knowledge of Jackson’s business matters, speaking on condition of anonymity because of the sensitive nature of the material, said in an interview with The Associated Press on Friday that there is a will. The Wall Street Journal reported Tuesday that the will splits Jackson’s estate between his three children, his mother and some charities.

“No one that I know of has ever seen the will,” Jackson family attorney Brian Oxman said on CBS’ “The Early Show” on Tuesday. “We simply don’t know.”

About the same time a judge granted Katherine Jackson authority over at least some of her son’s estate Monday, pickup trucks and a large dump truck towing a flatbed were seen entering the 2,500-acre Neverland Ranch, a major piece of the singer’s debt-strapped financial empire. It was not clear who had requested the fleet or for what purpose.

Clearly one of his most valuable assets is his recording catalog, which his father could potentially rerelease through his new record company if the family gains control of his assets. There could also be recordings in Jackson’s estate that he had never released.

There’s also a financial bonanza to be had in the Sony/ATV Music Publishing catalog of which Jackson owned 50 percent. The 750,000-song catalog includes music by the Beatles, Bob Dylan, Neil Diamond, Lady Gaga and the Jonas Brothers, and is estimated to be worth as much as $2 billion.

When Jackson died Thursday, he also left behind a 12-year-old son and 11-year-old daughter by his ex-wife Deborah Rowe, as well as a 7-year-old son born to a surrogate mother.

The Jackson family said the children — Michael Joseph Jackson Jr. (known as Prince Michael), Paris Michael Katherine Jackson and Prince Michael II — are living at the Jackson family compound in Los Angeles’ San Fernando Valley.

“They have a long established relationship with paternal grandmother and are comfortable in her care,” the family said in court documents.

Family patriarch Joe Jackson, 79, said at a news conference that the children were enjoying playing with other kids — something they do not normally do.