The founder's oldest child, Prime Minister Lee Hsien Loong, came under attack online before dawn from his younger brother Lee Hsien Yang, and younger sister Lee Wei Ling. They accused him of exploiting their father's legacy for his own political agenda, a charge the premier quickly denied.
The pair also claimed that their brother had abused his powers to harass them -- and Hsien Yang said he had decided to leave the country as a result.
The feud had simmered following the death in March 2015 of the elder Lee, who ruled Singapore with an iron hand but transformed the city-state from a relatively poor British colony into one of the world's wealthiest and most stable societies.
But the quarrel intensified in the small hours of Wednesday with the issuance of the extraordinary statement, which immediately went viral in a country where tough laws against protests and curbs on press freedom have stifled political dissent.
More than a family feud
"The timing is important as Singapore has been facing more uncertainty both in terms of the current and future leadership as well as the economy and regional situation," said Southeast Asia watcher Bridget Welsh, a visiting professor at John Cabot University in Rome.
"An attack from trusted family members is impactful and legitimately raises questions. Some will see this as a family squabble but it is clearly more than this," she told AFP.
"The effects are to raise questions about how Lee Hsien Loong is using his father's legacy... also attention will be brought to (Lee's) wife and her power and legacy... It will cause introspection about whether Singapore can be separated in the future from the Lee family."
The siblings' grievances largely centre on the fate of the family's home after their father's death.
The pair said their brother Lee had defied their father's instructions to tear it down.
A cabinet statement Wednesday said however that PM Lee has "recused himself from all government decisions" about the fate of the former family home.
Lee Hsien Loong's wife Ho Ching is the chief executive of state investment firm Temasek Holdings, which had global assets worth Sg$242 billion ($180 billion) as of March 2016.
"We have felt threatened by Hsien Loong's misuse of his position and influence over the Singapore government and its agencies to drive his personal agenda," read the statement posted online by his siblings.
Michael Barr, associate professor of international relations at Flinders University in Adelaide, said "normal people who try to do something similar would've been dealt with by the courts by now", referring to the strong criticism of Lee.
"Ultimately, how much damage to the Lee brand is done is another question," he added.
The prime minister, who is on vacation overseas, fired back with his own statement, saying he was "deeply saddened by the unfortunate allegations".
"Ho Ching and I deny these allegations, especially the absurd claim that I have political ambitions for my son," Lee said in a statement issued by his office.
The same statement was put up on Facebook where it gathered more than 17,000 reactions and 1,500 comments, mostly supporting him.
"Since my father's passing in March 2015, as the eldest son I have tried my best to resolve the issues among us... out of respect for our parents," he added. "My siblings' statement has hurt our father's legacy."
The premier's siblings also alleged they were being closely monitored, adding they had lost faith in their brother's ability to lead.
"We feel hugely uncomfortable and closely monitored in our own country," they said.
"We do not trust Hsien Loong as a brother or as a leader. We have lost confidence in him."
Hsien Yang, currently the chairman of aviation regulator Civil Aviation Authority of Singapore, added that he "will leave Singapore for the foreseeable future" over the widening rift.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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