The family lived in Antioch for three years, but the Foster arrangements among Shameeka Davis, Jazzmin and her brother were being supervised by the San Francisco Department of Child Protective Services.
In the meantime according to police, the autopsy on Jazzmin Davis has yet to reveal a specific cause of death, but it is clear that the girl suffered greatly before she died.
Antioch police say 15-year-old Jazzmin Davis had been severely beaten in the days and weeks leading up to her death.
"The autopsy did reveal severe child abuse, including being burned with hot irons at various locations on the victim's body," said Lt. Leonard Orman from Antioch Police. "She had also been whipped with numerous implements that included plastic belts, dress belts, canvas dress belts and electrical cords."
The woman now described as Jazzmin's foster mother, her biological aunt, Shameeka Davis remains in Contra Costa County Jail booked on charges including murder and three counts of corporal punishment causing great bodily harm.
Police say Jazzmin's twin brother, examined on Thursday at an area hospital, also showed signs of severe abuse similar to that of his sister.
And they released a photo of the children's biological father -- 40-year-old Jason Lawon Davis, who is the brother of Shameeka Davis.
He has a warrant out for him for a parole violation, on an unrelated matter.
"He's not a suspect in our case, we just want to talk to him, but the means for us to talk to him may be to take him into custody," said Lt. Orman.
Detectives say Shameeka Davis has admitted to them that she had abused Jazzmin and her brother.
"She talks about that fact that she does lose control," said Lt. Orman.
According to Antioch Police Shameeka Davis had been trying to adopt Jazzmin and her brother, but the process was never completed.
She was legally their foster parent, under the supervision of the San Francisco Department of Child Protective Services, and was receiving more than $13,000 per year from that agency for their support.
According to Antioch Police, the agency last sent a social worker to visit the family in Antioch in Setpember of 2007.
Joe Valentine is the director of Contra Costa Social Services, which oversees Child Protective Services.
"If she was a foster parent, a social worker would be visiting the home every month," said Valentine.
ABC7 News spoke with a representative from San Francisco's Department of Child Protective Services regarding what Antioch Police had said about the children's visitations. "So in 1993 when the babies were placed we visited monthly, but when the case comes to a certain point in time and when there is an element of stability and well-being for the children, then we very much scale back to six months," said San Francisco Human Services Executive Director Trent Rhorer.
The state Department of Social Services said there are exceptions to the monthly visitations requirements for families. For instance, when a child is in a long-term "stable placement," and according to San Francisco officials the twins had been with Shameeka Davis since they were babies and Shameeka Davis obtained legal guardianship of the kids on August 27, 2008.