The filings do not mention Love or give a reason for the guardianship.
A three-page order issued Friday is all that is publicly available.
Attorney Geraldine Wyle, who is handling the case for the mother and sister, calls it a private family matter and said no other comment would be issued.
An e-mail message to Love's publicist Alan Nierob seeking comment was not immediately returned Monday.
The court order, which is valid until February, grants Cobain's mother and sister no control over a trust established by the Nirvana frontman for his daughter.
The guardianship was first reported by TMZ.com.