Attorneys representing two people claiming to be among Prince’s heirs have filed a constitutional challenge to the requirement that they substantiate their claims with genetic evidence.

Their attorneys say the requirement violates the equal protection clauses of the Minnesota and U.S. constitutions.

The objection, made public Friday in Carver County District Court, was filed on behalf of Brianna and Victoria Nelson, who claim they are Prince’s niece and grandniece, respectively.

They are the daughter and granddaughter of the late Duane Nelson Sr., whom they contend was one of Prince’s half-siblings.

Prince died April 21 of an accidental overdose of fentanyl, a powerful opioid painkiller.

Because no will has been found, Minnesota law determines how his vast estate, estimated at $100 million to $300 million before taxes, will be distributed.

Carver County District Judge Kevin Eide has certified as presumptive heirs Prince’s sister, Tyka Nelson, and his half-siblings, Sharon, Norrine and John Rodger Nelson, Alfred Jackson and Omarr Baker.

Some have challenged assertions that Duane Nelson was actually one of Prince’s half-siblings. Eide ordered Brianna and Victoria Nelson to prove their claims with genetic testing.

“The Minnesota Probate Code does not limit heirs in this way. Even if the Probate Code did permit such limitations, the protocol’s blanket exclusion of entire classes of family relationships violates the fundamental protections of due process and equal protection accorded by the U.S. Constitution,” their attorneys wrote.

They argue that Prince referred to Duane as his brother and that no sibling had a closer relationship to him. John L. Nelson’s name appears as father on both Prince’s and Duane’s birth certificates, though they were born a few months apart to different women. The two hung out together in high school, and Prince put Duane in charge of his personal security detail until mental illness caused his behavior to deteriorate, the lawyers say.

The court-approved protocol for establishing heirship fails to recognize family relationships like the one Duane had with the late musician, they wrote.

“The proposed protocol does not recognize that John Nelson held out Duane as his son,” they said.