An arrest warrant has been issued for the biological mother of three children police said were taken against their will.
Miami-Dade school police said Carrie Weingarth is being sought on a charge of interference with custody.
Federal prosecutors also issued arrest warrants for Weingarth and her boyfriend, Christian Coello, on charges of unlawful flight to avoid prosecution.
Police said Erin Pena, 12, Steven Pena, 8, and Derick Pena, 7, were abducted from Gulfstream Elementary School during lunch last Friday. Police said Weingarth was last seen traveling west in a 2014 Jeep Patriot with the children in the Walker, La., area. Police said the Jeep was rented in Jacksonville.
"Carrie, I just want you to come home and I want your kids to be safe," Melissa Weingarth said of her sister at a news conference Thursday morning.
The family has hired a private investigator to help find Carrie Weingarth and bring her home.
"I know that Carrie loves her children very much and would not hurt them," private investigator Joe Carillo said.
Carillo described the 32-year-old Homestead woman as a mother who has struggled to provide for her children and was denied financial assistance.
"You don't know, but Carrie used to have to go to the library up the street to feed her kids sometimes because she received no assistance from anybody other than her family," Carillo said.
Until this week, Carrie Weingarth did not have custody of the oldest child, but a court recently granted her custody of all three.
"We just want to help you," Melissa Weingarth said. "We want to make things better, so please come home."
Anyone with information as to their whereabouts is asked to call police 305-995-1553.