Patrick Maughan, 36, a labourer, drew up in his van to see the blackened shell of the council maisonette he shared with his wife, three sons and daughter at Kings Heath, Birmingham.
Police had tried for seven hours to trace him and issued an appeal on local radio.
Mr Maughan's wife Debra, 26, survived the blaze. Last night they were being comforted by relatives.
The fire broke out in an upstairs bedroom shortly before 9am. The children, Sharon, five, Francis four, Martin, three, and Stefan, 18 months, were overcome by smoke. Martin was revived but died later in hospital.
The others were certified dead at the scene.
The children's 25 year-old uncle, Christopher Finn, who was also trapped in the blaze, was last night said to be in a critical condition in hospital.
Three police officers armed with a fire extinguisher crawled into the house to try to rescue the children before firefighters were able to bring them out.
An Assistant Chief Fire Officer, Michael Lyons, said it was too early to say what had caused the fire, which started in a small box room at the back of the house.