The investigation was continuing into whether the deaths were accidental or may have been the result of a murder-suicide, according to a statement from Miami-Dade County police.
"It's too early to know what happened," said police Detective Nelda Fonticiella.
The dead adults were identified as Robert Perez, 37; his wife, 33-year-old Maytee Marquez; and Marquez's mother, 56-year-old Maria Lucas. The body of Marquez was found inside a green Ford Explorer in the home's garage that was still running Sunday.
The two children were identified as half-brothers Christopher Perez, 13, and 10-year-old Nestor Perez. Marquez was Nestor's mother and Christopher's stepmother, Fonticiella said.
Autopsies will be performed to determine the precise cause of death, the police statement said.