More possible heirs to late music legend Prince emerged Thursday, including a child who may be his grandniece, according to a letter filed with a Minnesota court. An attorney said the girl, identified as a V.N., a minor, is the daughter of the son of Duane Joseph Nelson Sr., who he said is Prince's half-brother. Duane Joseph Nelson, Sr., died in 2011. He also had a daughter, Brianna Nelson, who could also be an heir, attorney Michael B. Padden said in a letter to a Carver County court Thursday. "I believe that under Minnesota law, his children and grandchildren would be considered heirs for this pending estate," Padden said in the letter. V.N.'s father, Duane Joseph Nelson Jr., died in 2005, Padden said in the letter. Padden acknowledged that Prince's family has not listed Nelson Sr. as a potential heir, but said he is a half-sibling and pointed to an alleged social media post from Prince's sister, Tyka, that indicates she considered him a brother. Padden said Duane Joseph Nelson Sr. and Prince grew up together but were estranged. Padden said he used to represent V.N.'s mother, but has been unable to contact her. RELATED: Warrant names doctor treating Prince before his death The letter asks that a guardian ad litem be appointed if V.N.'s mother does not hire an attorney to represent the claim. Prince was found dead at his Paisley Park estate on April 21 at the age of 57. Prince's sister said it does not appear that he had a will. His estate is said to be worth $300 million. A representative for Prince's family said this week they are not commenting on potential heirs. On Monday, an attorney representing Carlin Q. Williams filed a letter claiming Williamsis Prince's son and seeking genetic testing to prove it. In a separate proceeding, a Minnesota judge last week authorized the administrator of Prince's estate to test a sample of Prince's blood in case any "parentage issues" arise. Prince's only known child, a son named Boy Gregory, died a week after being born in 1996. This story originally appeared on NBCNews.com.