"The kids were everything to Michael. They were his whole life," Lester added.
Who will get guardianship of the kids is the latest in a series of questions that have surrounded Jackson's children -- regarding their conception, paternity and the way in which their father has raised them, since his first son's birth in 1997.
That son is Prince Michael Jr., 12, who along with daughter Paris Katherine, 11, were born to Debbie Rowe, a nurse in the office of Jackson's dermatologist Dr. Arnold Klein. In February 2008, Rowe told British newspaper the Daily Mail that she had been artificially inseminated but would not give details concerning whether the sperm used belonged to Jackson or another man.
In photographs, the children appear to have distinctly white skin.
The couple was briefly married following Prince's conception, but divorced six months after Paris' birth. Rowe gave Jackson custody of the children, but sued him in 2006 for breach of contract in an attempt to regain custody. The pair settled out of court for undisclosed terms and Jackson retained custody.
According to Brown, the Jackson family believes Rowe will again try to gain custody of her children. Other sources say she would like to be a part of the kids' lives and may go to court if it comes to that.
Rowe's lawyer, Iris Finsilver, would not comment on Friday on whether Jackson's ex-wife would try to get custody of the children after Jackson's death, saying only: "Debbie is absolutely inconsolable."
But another attorney for Rowe, Marta Almli, said in a statement to the press on Saturday: "Ms. Rowe's only thoughts at this time have been regarding the devastating loss Michael's family has suffered. Ms. Rowe requests that Michael's family, and particularly the children, be spared such harmful, sensationalist speculation and that they be able to say goodbye to their loved one in peace."
In 2001, Jackson had a third child, a son named Prince Michael II, better known as Blanket, who was carried by a surrogate mother whose name has not be released.
Jackson later admitted making a "terrible mistake" when he dangled his infant son over a hotel balcony in Berlin as he greeted screaming fans. A year after, following a stunning admission in a television interview that Jackson invited an unrelated adolescent boy to share his bed and offered him wine -- which he called "Jesus juice" -- the pop star was accused of molesting the child.
In between the interview and the 2005 molestation trial, California state child welfare officials interviewed Jackson's children and Rwaramba, the nanny originally from Rwanda.
Jackson was acquitted of the charges in the trial. No further molestation charges were brought against him and he retained custody of his children.
During the investigation, Jackson's parents Joe and Katherine told ABC's Barbara Walters that they were concerned officials would attempt to take away the children. They offered to adopt the children, should the singer lose custody of them.
According to Brown, Jackson said he wanted Grace Rwaramba to have custody.
"Michael's wishes were known. He wants Grace to have the kids. They love her," Brown said.
"If the kids had the choice," Brown said, "I think they'd pick Grace."
Before his death, Jackson was in regular contact with his mother but had a notoriously contentious relationship with his father.