The ages of the children and their relationship to the two adult women found at a Bedford home in Perth's east were confirmed on Monday by WA Police.
Neighbours watched on as forensic officers and homicide squad detectives descended on their quiet suburban street and started to lock down the home for further investigation.
Police attended a home on the corner of Fort Street and Coode Street in Bedford around midday on Sunday after a man presented himself to a regional Western Australian police station early that morning, Assistant Commissioner Paul Steel told reporters.
Police say there are no on-going concerns for public safety as a result of this incident.
"This is a very close community", she said.
Police said a search was launched after an unnamed man in his 20s provided information to the police.
POLICE have charged a 24-year-old man from Bedford with five counts of murder over the deaths of two women and three children.
A distraught neighbour told WA Today that she often saw children playing in the front yard of the house at the center of police investigations.
Ms Harvey and Mr Harvey both used to work for a Sino Steel Pilbara mine, and Ms Harvey sold some of her properties to help her partner start up a business.
Maria Manfredini, who has lived in the area for more than 30 years, said it was tragic on every level.
"Just a normal family, you would never imagine anything like that happening", he said.
"It's taken us by complete shock", she said.
No charges have been laid yet and it is unclear whether the man is related to the victims.
Peter Miles, 61, his 58-year-old wife Cynda, their daughter Katrina, 35, and her four children - daughter Taye, 13, and sons Rylan, 12, Arye, 10, and Kadyn, eight - were found dead at their Forever Dreaming Farm in Osmington on May 11.
A forensic team will be investigating the scene.
In July, Kiwi mum Michelle Peterson, 48, and her children Bella, 15 and Rua, 8, were killed in the suburb of Ellenbrook.
A police officer stands outside a property where five people were found dead in a suburb of Perth, Australia, September 9, 2018.