LOS ANGELES -- The fate of Michael Jackson's three children remained unclear Friday as reports raised the possibility of a custody battle involving the biological mother of the late star's eldest offspring.

The three children -- Prince Michael, 12, Paris, 11, and Prince Michael II, 7 -- were reported to be in the care of Jackson's mother Katherine at the family estate in Los Angeles as the musical clan mourned.

Jackson's former wife of three years Debbie Rowe is the mother of the two eldest children, while the third was born in 2002 to a surrogate whose identity has never been made public.

There were conflicting reports over whether Rowe, who separated from Jackson in October 1999, had signed away her parental rights.

TMZ.com website cited a lawyer familiar with the case as saying that Rowe had never had her parental rights legally terminated, which could clear the way for her to gain custody and win a multi-million-dollar settlement.

However Jackson family lawyer Brian Oxman was quoted as saying that the children would likely be looked after by Katherine Jackson.

"Probably Mrs Jackson will take care of them, she loves them dearly," Oxman told the celebrity website Radaronline.

Gloria Allred, a celebrity lawyer told CNN she was "very concerned" about Jackson's children. "What will happen to them?" she said. "If the mother relinquished parental rights then who's to have custody?"

But family law attorney Fred Silberberg told Agence France-Presse that Rowe stood an excellent chance of securing custody of Prince Michael and Paris.

"Generally speaking in California, biology trumps everything," Silberberg said.

"Courts tend to favor the biological parents so in that regard she has a very strong case," Silberberg said, drawing comparisons to O.J Simpson, who successfully saw off a custody challenge from the grandparents of ex-wife Nicole Brown-Simpson, who he was accused of murdering in 1994.

Another Jackson confidante, new age guru Deepak Chopra, told CNN he was concerned the three siblings -- the two children Jackson had with Rowe and their half-brother Michael -- could be split up by a custody battle.

"Well, they're going to be separated I fear, unfortunately," Chopra said.

Scott Altman, a professor at the University of Southern California and an expert in family law, said any custody claim by Rowe could hinge on what had been agreed with Jackson at an earlier hearing.

"She signed an agreement purporting to give up her parental rights but then more recently she went to court to seek custody and succeeded having that agreement declared invalid," Altman said.

"Ultimately they settled that legal disagreement, and she did not pursue a final custody decree. She could come forward and seek custody as a legal parent to the children."

If Rowe's custody claims were challenged by Jackson's family and the case went to trial, much would depend on details of the children's relationship with Rowe that remained opaque, Altman said.

"There are a lot of factual details we just don't know about -- how much contact has she [Rowe] actually had with these children over the years? What is the nature of their relationship at a social level? Are the children close to her on a psychological level?"

"The answers to those questions may make it more or less difficult for her to get custody," he said.

"In the end, the children's own preferences could decide the issue," he said.

"My assumption is that if this gets to trial a great deal is going to turn on expert psychological testimony about the children's relationship with the various caretakers involved and the judge's impression of that and potentially the children's own preferences," Altman said.

Meanwhile, even less was known about the surrogate mother of Jackson's youngest child, Prince Michael II, or "Blanket," who was famously dangled from a fourth floor window in Berlin by his late father in 2002.

"I don't think they know much about who she is and whether she'll come forward," Altman said.

"I gather she was a surrogate but we don't know anything about the legal arrangements or whether she's had any contact with the child."

Allred told the momlogic.com website that Jackson's will could determine where Prince Michael II ends up.

"With the third child, the issue is guardianship -- who will have guardianship of the child. Maybe Michael Jackson indicated a preference, but just because he indicated a preference, a court is not bound by that preference," Allred said.

"You cannot will a child like a piece of property, or piece of jewelry -- a child is a human being."