People.com said it was not immediately clear why Love, a recovering drug addict, lost guardianship of her daughter.
The report said Cobain's mother, Wendy O'Connor, and his sister, Kimberly, were granted legal, medical and financial authority over Cobain's daughter until at least Feb. 10, when a court hearing is scheduled.
"This doesn't necessarily mean that Courtney Love is an unfit mother and has completely lost custody," Los Angeles probate attorney Jeffrey S. Cohen, who is not involved with the case, told People.com. "It's too early to say. It could be because she's simply going out of state for a long period of time."
Cobain committed suicide by shooting himself in 1994 at age 27.