The younger siblings of Prime Minister Lee Hsien Loong accused him of misleading their father, founding prime minister Lee Kuan Yew, over the status of the family home.
They claimed that PM Lee had given their father the impression that the gazetting of 38, Oxley Road was either "inevitable" or that the house was already gazetted.
Because of the "misrepresentation", Mr Lee Kuan Yew, who had wanted to demolish the house, had considered "alternatives" to demolition, Mr Lee Hsien Yang and Dr Lee Wei Ling said.
In Parliament on Monday, PM Lee had revealed that his father had approved of renovation plans to the house, which would involve demolishing the private living spaces but preserving the basement dining room which had historical significance.
He said this showed that while Mr Lee wanted to demolish the house, he was prepared to consider other options, if the Government decided otherwise.
The younger Lee siblings alleged that their brother wanted to preserve the house for political gain.
PM Lee has denied this.
In a Facebook post yesterday morning, which he said was also on behalf of his sister, Mr Lee Hsien Yang wrote: "From 2010, LHL improperly misrepresented to our father LKY that gazetting of 38, Oxley Road was either 'inevitable' or that the house was already gazetted. We now know that no decision had been made."
Mr Lee Hsien Yang cited an e-mail dated Oct 3, 2011, from their father to all three Lee siblings as well as PM Lee's wife Ho Ching, in which the patriarch wrote that "Loong as PM has indicated that he will declare it a heritage site. That will put an end to any rebuilding".
This was proof that their father was sceptical about the renovation plans, said Mr Lee Hsien Yang, as it would be inconsistent with PM Lee's insistence that the house would be gazetted.
He added: "In Parliament, LHL has tried to play with words, asserting that just because Lee Kuan Yew left instructions for what to do if the house was gazetted, that means that he 'accepted' that the house should be gazetted."
He said that leaving instructions for how to deal with a "bad event" did not imply acceptance or desire for such an outcome.
"Suppose someone leaves instructions saying, 'I don't want my books to catch fire. But if my books do catch fire, please call my insurance company.'
"That does not mean that he 'accepts' that his books will catch fire. Obviously, it is not an excuse to burn his books."