Anthony Robert Harvey, 24, is accused of killing his twin two-year-old girls, his three-year-old daughter, his partner and his mother-in-law.
Their bodies were found at the Coode St home on Sunday after Harvey visited a local police station.
The tragedy has stunned neighbours, who haven't seen the family in over a week.
"We thought they were on holiday, they haven't been there all week," Desrae Cambos told 7 News.
One neighbour told WA Today she often saw children playing in front of the house.