The father of two boys found dead in their family home in the Blue Mountains says the incident has caused "unimaginable pain" as the siblings' mother remains in hospital under police guard.
Nick Smith discovered the bodies of his two sons, Russell, 11, and Ben, nine, at their Faulconbridge family home on Tuesday.
Police are waiting to question their 42-year-old mother, who was separated from Mr Smith, after she was taken from the scene to hospital with minor injuries.
In a statement on Thursday, Mr Smith expressed his disbelief at the tragedy while also calling for privacy.
"The loss of our two beautiful boys has caused unimaginable pain and distress," he said.
"Russell and Ben were happy, funny, outgoing boys and were very much loved by their family and friends."
Mr Smith said his sons loved sports, soccer, the Penrith Panthers, fishing, as well as spending time with friends and their dog Max.
"We cannot understand how our boys have been taken this way and we appreciate the kindness and compassion shown by the community," he said.
"We also ask the media respects our need for privacy at this time and give us the time and space we need to grieve."
Flowers, teddy bears and toy cars were propped against the fence of the Faulconbridge home as a photo of the smiling, dark-haired siblings was publicly released by their family on Wednesday.
The mother's personal Facebook page is filled with photos of her and the children together, showing them on frequent bushwalks and beach visits.
Investigators have declined to speculate on what occurred before the brothers were killed but police have said they are not looking for any other parties.
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