Police believe a mother stabbed two of her children and set her house on fire during a family dispute that killed all four people inside the Heidelberg Heights home on Sunday.

Police revealed today that those killed in the blaze were a 36-year-old mother and her three children - an 18-year-old woman, a girl, 13, and a boy, 11.

A flower on the front fence of the Heidelberg Heights house in which four people died. Credit:Craig Abraham

The bodies of the 18-year-old woman and 11-year-old boy suffered wounds consistent with being stabbed with a sharp object, according to a police statement today.

The eldest daughter's boyfriend saw her bleeding heavily after a fight with her mother moments before the house erupted in flames.