Father's heartache after Cairns stabbing deaths

He should be celebrating his daughter's 14th birthday but a Cairns father is instead grief-stricken and in shock, trying to make sense of her tragic death.

"I've lost a beautiful daughter," the elderly man told AAP.

"What for? What has she done?"

He says tears streamed down his face when he and his wife were told their girl was one of eight children found murdered at a house on Murray St in the Cairns suburb of Manoora yesterday morning.

Mersane Warria, the 37-year-old mother of the other seven children, who were aged between 18 months and 14 years, has been arrested and is under police guard in hospital where she is being treated for stab wounds. Their bodies were found by her 20-year-old son on Friday.

The father said his daughter had been staying with the woman, the girl's aunt, in the Murray St house for about a week.

"(The son) told us that everyone is dead," he said.

"I said how come you are telling me this.

"And I was crying and (my wife) was crying, everybody was crying."

He last saw his daughter the night before she died at a local McDonald's restaurant where she was eating dinner with friends.

"I said come with me but she said: `Oh no dad, I'm going with my friends, my aunty,'" he told AAP.

The man said he and his wife are now searching for answers.

"What happened?" he said.

"Do you know what happened? Me and my wife we want to know."

He was shocked by news the aunty may be responsible.

The man said his daughter had spent many weekends and holidays at the house and there had never been problems.

He said Warria had recently decided to turn her life around and was again attending church.

He said his daughter loved her friends, school and reading.

"When I dropped her at the house a week ago, everyone was happy," he said.

"The last time I saw her she kissed me. She said she loved me and she asked for $100 which I said I'd give to her on Saturday morning on her birthday.

"My daughter, she was beautiful."