By Curtis Skinner and Steve Gorman

(Reuters) - A Minnesota judge has excluded nearly 30 would-be heirs from the estate of the late pop star Prince, bolstering the inheritance claims of the performer's sister and surviving half-siblings, probate court records released on Friday showed.

The court order, issued on Thursday, came in response to a flood of individuals seeking a piece of an estate some have valued at more than $500 million, left by Prince when he died unexpectedly in April at the age of 57, apparently without a will.

Claims have poured into the probate court since Prince's younger sister, Tyka Nelson, filed a petition seeking appointment of a special administrator for the estate and naming herself and five half-siblings as the only known heirs.

In his 19-page order, Carver County Judge Kevin Eide appeared to accept those six claims, stating, "The court is not aware of any objection or dispute with the statement that these persons are the siblings or half-siblings" of Prince.

Under the ruling, Tyka Nelson and three half-siblings by Prince's father will undergo genetic testing - John, Norrine and Sharon Nelson - along with two more individuals claiming to be Prince's niece and grandniece.

No provision for genetic testing was made for two other half-brothers - Alfred Jackson and Omar Baker - who shared a common mother with the singer.

The judge dismissed claims of heirship from a total of 29 other people purported to have some degree of kinship with Prince, including a professed secret wife who said the CIA had classified their marriage records as top secret.

Among other would-be heirs he denied were five people who came forward claiming Prince was their biological or adoptive father, and several others claiming their dad was also Prince's genetic parent by way of an extramarital affair with his mother.

Also dismissed were a batch of claims by several people who described themselves as descendants of a sister of Prince's great-grandfather.

The musician, born as Prince Rogers Nelson, has long been identified in public records as the only surviving son from the marriage between Mattie Della Shaw and John L. Nelson, both of whom are now dead. And Judge Eide ruled there was no "credible, documented claim" of a surviving Prince spouse.

If Prince also left no will and no surviving offspring of his own, as appears to be the case, his estate under Minnesota law would be apportioned in equal shares to his siblings and the nearest surviving descendants of any siblings now dead. Siblings and half-siblings are treated the same.

The special administrator of the estate, Bremer Trust, has said it was in the process of determining the fair-market value of Prince's estate.

(Reporting by Curtis Skinner in San Francisco and Steve Gorman in Los Angeles; Editing by Frances Kerry, Bill Trott and Bernard Orr)