The 45-year-old woman and her 19-year-old daughter will each be charged with five counts of homicide and one count of conspiracy, according to the district attorney's office.
District Attorney Matthew Weintraub said the mother and the daughter were the residents of the apartment in which the five relatives were found. Weintraub said in a press conference that the deceased included two children, her sister, and her sister's 9-year-old twin daughters.
"This is a terrible tragedy," he said. "I just spoke to the family of all five of the deceased and we're all heartbroken."
"I wish I had better news to report but this is important, so we wanted to come out … and make sure Everybody knew that the people who committed these atrocious acts are now in detention and will be made to pay for their crimes, "he said.
Weintraub said there is an ongoing investigation into how the victims died.