In the legal document signed Sunday and obtained by PEOPLE, Johnston – who is not listed as an heir in court documents – says she is an "interested party" and also consents to the "appointment of Bremer Trust, National Assocation as Special Administrator for the Estate." The court will have the final say on the legitimacy of Johnston's claim.
According to TMZ, Johnston has a different father than Prince, and some members of his family "only learned of Darcell's existence a few days ago."
On Monday morning, Prince's sister Tyka Nelson and four of the singer's half-siblings met in court for a hearing about the music legend's reported $250 million estate.
A lawyer for Bremer Bank and Trust – the institution appointed to handle the estate – said the bank is continuing to search for a will.
"We are not finding that there's no will, but that no will has yet been found," Judge Kevin W. Eidge said.
On April 26, Tyka Nelson filed an emergency petition that named herself and the singer's five known half-siblings as potential heirs to his estate.
If it is discovered Prince indeed had no will, his estate is expected to be split equally among his surviving siblings under Minnesota law.