The little face of a family house fire tragedy

The family of a four-year-old boy killed in a house fire in Perth's south-east has released a photo of him.

Tyhreese Alaniz celebrated his fourth birthday days before he died as a result of smoke inhalation from the Thornlie house fire.

His great grandfather Hugo Alaniz, who raised the boy since he was a baby, was also killed.

Both were pulled from the burning home by firefighters on Wednesday night and taken to hospital but couldn't be saved.

69-year-old Hugo passed away on Wednesday, his great grandson clung to life until Thursday afternoon.

The Alaniz family has paid tribute to both family members saying they were extremely close and Hugo would walk Thyreese to kindergarten every day.

The family said in a statement that Mr Alaniz and Tyhreese will be together for their funerals after the young boy's organs have been donated.

"Their wish is for Hugo and Tyhreese to be together on their final journey," the statement said.

"But naturally with the careful and thorough nature of the organ donation process, there is uncertainty in relation to timing which is causing distress.

"The Alaniz family would like the recipients to know that Thyreese’s organs come with their blessings and would like those recipients to live a full and happy life.

"The Alaniz family encourage others to talk about organ donation, it is an opportunity for other families to enjoy the quality of life that Australia has given to them.”

The fire is not being treated as suspicious.

The cause is still under investigation.