The latest revelation in the murder and corruption scandal, which brought Bo down and exposed deep divisions in China's ruling Communist Party ahead of a once-in-a-decade leadership change, came from Bo's ex-wife Li Danyu.
She told the New York Times - which described the saga as 'Shakespearean' - that months before Bo fell, he told her brother he had forensic evidence of a plot to kill Gu, his current wife.
Bo reportedly said he suspected mastermind was his own son with Li, Li Wangzhi who is also known as Brendan Li. He is a graduate of Columbia University and works in finance in Bejing.
The US daily said Bo's brother-in-law described the suspicions as outlandish and the politician appeared relieved.
Li Danyu said she believed the source of the accusations against her son was Gu herself. "She can be that paranoid," the paper quoted her as saying.
Official accounts of Gu's conviction for poisoning Briton Neil Heywood said she believed he was a threat to her own son Bo Guagua. She was given a suspended death sentence, which is normally commuted to life in prison.
The charges against her became public earlier this year after Bo's former key aide and Chongqing police chief Wang Lijun fled to a US consulate to seek asylum.