The fire started around 12:45 a.m. Saturday on the unit block of Bradly Road in New Castle.
Firefighters arrived to the house totally engulfed in flames.
A man, woman and their two children were inside, but managed to escape.
The parents are OK, but the children were taken to Christiana Hospital for smoke inhalation. No word on their conditions.
The fire was placed under control within an hour.
There is no immediate word on the cause of the blaze.