Flames tore through their 1920s semi-detached property in Chapel Road on Saturday night.
All four occupants escaped from the two-storey building after fire broke out in an upstairs bedroom.
The man was taken to the Queen Elizabeth Hospital, to be treated for smoke inhalation, while the woman, a boy and a girl were put up in a nearby hotel.
Neighbour Charlie Howling is collecting children's clothes, toiletries, food and money on their behalf.
She said they fled the blaze with just the clothes they were wearing, leaving almost everything else behind them.
'I'm going to be doing my best to get them what I can,' she said. 'It's been pretty bad for them.'
Miss Howling said Tesco in King's Lynn had donated some children's clothes, while a well-wisher had delivered toiletries to the hotel where the woman and children are staying. Both pubs in Terrington have also agreed to have collecting boxes.
Crews from Kings Lynn, including an aerial ladder platform, attended Saturday night's blaze, along with crews from West Walton and Wisbech. Firefighters used breathing apparatus, hose reel jets and a fan to ventilate smoke from the property.
An ambulance spokesman said: 'We were called at just before 11.30pm to Chapel Road, Terrington St Clement, to a report of four people with smoke inhalation. Two ambulance crews, an ambulance officer and hazardous area response team attended.
'One patient was taken to Queen Elizabeth Hospital for further treatment. Three patients were treated at the scene, but were not taken to hospital.'
Neighbours said the alarm was raised just after 11pm. One said: 'We could hear noise but we wouldn't quite hear what it was.
'Then they banged on the door and said the house was on fire and told us to get out, they said they'd called the fire brigade.
'We had three fire engines, ambulance, police. One went to hospital, the others were put up in a hotel.'
Another said: 'It started in the bedroom, the whole upstairs was completely destroyed.'
If you would like to donate, e-mail charlie.howling@yahoo.co.uk.
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