The medical examiner's office has identified the victims as Chloe Tse, 1, and her 33-year-old father Raymond Tse, both San Francisco residents.
The blaze was reported around 1:30 a.m. at 1986 18th Ave., fire spokeswoman Mindy Talmadge said.
Firefighters responded and found the father downstairs. He was in full cardiac arrest and was pronounced dead at the scene, Talmadge said.
Fire crews went upstairs and found the young girl in a bathroom. She also succumbed to her injuries, Talmadge said.
Chloe's grandfather was taken to the hospital with critical injuries and later died at the hospital Friday night. Her mom was also hospitalized with moderate smoke inhalation, according to Talmadge.
Firefighters eventually extinguished the blaze at 2:01 a.m., she said.
The cause of the fire remains under investigation but it is not considered suspicious, Talmadge said. The house had working smoke alarms, she said.