Anthony Robert Harvey pleads guilty to murdering family in Perth

A Perth father has pleaded guilty to massacring five members of his own family at their Bedford home last year.

Anthony Harvey, 25, murdered his wife Mara, their three-year-old daughter Charlotte and two-year old twins Beatrix and Alex on September 3, before killing his mother-in-law Beverly Quinn the following day.

Police alleged Harvey spent several days in the house with the bodies, before travelling to a remote northern WA town, where he handed himself in.

They said a blunt instrument and knives were used in the murders.

Harvey kept his head down as he pleaded guilty to five counts of murder in the WA Supreme Court.

He will be sentenced on June 21.

Relatives of the Quinns spoke of their grief following the tragedy last year.

In a statement given to WA police in September Ms Harvey's sister and Ms Quinn's daughter Taryn thanked everyone who had helped them through the difficult time and paid tribute to their loved ones.

She described Charlotte as an "energetic, bubbly confident little girl", while "Alice was outgoing, adventurous and cheeky" and "Beatrix was at times a little bit more quiet but gave the biggest hugs".

Taryn said her sister "loved being a mum and she loved her girls".

"She was so proud of each of them and was doing a great job of raising them. Her girls were her world," the statement read.

Ms Quinn was remembered as "a kind hearted, caring mother and grandmother".