Four-year-old dies from injuries after shed fire at Victorian home

The brother of two children who were killed in a horror shed fire in Corio near Geelong has also died in hospital.

Four-year-old Isaac suffered extensive burns after heroically shielding his siblings, three-year-old Saige and 18-month-old Ashlynn, when fire erupted on the family property on Sunday.

The only surviving child, six-year-old Mavis, remains in a critical condition at the Royal Children's Hospital.

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The children's father Kane McGregor told media yesterday that his family had experienced the worst two days of their lives.

He described Isaac as one of the "strongest children (he) has known".

"Isaac had two huddled under him so they didn't burn," he said.

"He stayed there until he died himself, (paramedics) revived him and flew him to (hospital)."

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Issac had suffered burns to 82 per cent of his body.

Their mother Jasmine Beck also received burns to her hands after dragging her children out of the blaze.

It's understood all four children were inside the shed playing together when a couch caught alight.

Police are continuing to investigate the cause of the fire, with McGregor saying a "clicky lighter" could be to blame.