A 69-year-old man who died in a house fire in Perth's south-east was the president of an organisation which represents exiled workers from Chile.

Hugo Alaniz was pulled from the burning house on Rushbrook Way in Thornlie on Wednesday night, along with his four-year-old great-grandson Thyreese.

The pair were rushed to Fiona Stanley Hospital, but Mr Alaniz could not be saved.

Neighbours said the fatal blaze quickly took hold of the house before fire crews arrived. ( ABC News: James Carmody )

Thyreese was transferred to Perth Children's Hospital, but died on Thursday afternoon.

His family have decided to donate his organs.

Mr Alaniz was well known in Chile for standing up for workers' rights during the Pinochet regime, and was jailed on several occasions over his connections to the union movement.

Mr Alaniz was jailed on several occasions in Chile under the Pinochet regime. ( Facebook: Paulina Godoy Ortiz )

He fled to Australia as a political refugee in 1985 alongside thousands of other Chileans.

His friend and colleague Wilson Cortes described him as an extraordinary man.

"He was a very good person, he was very charismatic," Mr Cortes said.

"He was very friendly all the time smile on the face, there never was a problem."

Chilean community to rally around stricken family

Mr Cortes first met Mr Alaniz when he was 25 and worked with him at a copper mine about 800km from Santiago, later becoming close friends in Perth.

He said even from Australia, Mr Alaniz fought for the rights of Chileans, leading a movement which led to a law change in Chile in 2004, allowing exiled refugees to apply for a pension.

He was the longtime president of DECOCHI (Departed from the Copper of Chile), an organisation created to fight for the rights of exiled Chilean workers.

Mr Alaniz's friend Wilson Cortes said the local Chilean community would support the family. ( ABC News: Kathryn Diss )

"He was a man who was born to be a leader. All the time he was involved, since very young, involved in fighting for the right of the worker," Mr Cortes said.

"He was involved in DECOCHI and our mission was fighting for our rights in Chile to try and recover what we lost over there."

Mr Cortes expressed condolences to the Alaniz family.

"As a community we are shocked, we feel so sad, because we know Hugo, we are friends, we are very close," he said.

"We are with them.

"As a community we support them, we are with them, and then whatever they want to do we support them 100 per cent."