Firefighters responding to the blaze around 6 a.m. found the three victims in the home within minutes.
The Fire Department says 32-year-old Cheryl Strong and 16 year-old Michael Fox died at the scene. Eight-year-old Kelsey Fox died at a hospital.
Daniel Fox, the children's father and Strong's boyfriend, told authorities he woke up hearing the kids screaming. He says he ran into the bathroom to try to open a window. The door shut behind him and he couldn't open it because it had no doorknob.
Fire officials say the kids were overcome by smoke while trying to save their father. The 37-year-old Fox says he broke the window and climbed out.