A trust fund set up for Prince, Paris and Prince Michael II - also known as Blanket - currently lies empty as lawyers organise the late singer's debts and legal bills, The Sun reports.
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It could be up to five years before they receive any money, with the youngsters currently living on an allowance controlled by estate executors and overseen by a judge.
Estate lawyer Howard Weitzman said: "The probate is still pending, and although almost all of Michael's personal debt has been or is about to be paid in full, the estate is technically still in debt.
"Once all of the creditors' claims, taxes and pending litigations have been resolved, the trusts will be funded per court order.
"It's too early to speculate on any precise number for a value. It will be a substantial number, I'm certain."
Michael's mother Katherine, who is entitled to half of the Michael Jackson Family Trust, is also yet to receive any cash.
Michael's siblings Randy, Jermaine, Janet and Rebbie demanded estate executors John Branca and John McClain resign earlier this year, claiming that they were withholding money from the Jackson family.
Prince, Paris and Prince Michael II will have to wait until they are 21 to access the fortune. They will then receive lump sums at the ages of 30, 35 and 40.
They recently visited their late father's childhood home to mark his birthday.