SINGAPORE - More questions have emerged over the final will of the late Mr Lee Kuan Yew, after his younger son Hsien Yang asserted that his father gave "express instruction" for the last will to follow the first version.

In a Facebook post on Saturday (June 17), Mr Lee Hsien Yang wrote: "Lee Kuan Yew's final will in December 2013 was engrossed on the basis of his express instruction to revert to his first will from 2011."

He added that his father's final will "was simply Lee Kuan Yew's first will of Aug 20, 2011, re-executed on his instructions".

The preparation of the late Mr Lee's last will has emerged as a main point of contention in the ongoing feud between the Lee siblings over their father's house at 38, Oxley Road.

Prime Minister Lee Hsien Loong earlier said their father's seventh and final will was made in troubling circumstances, and asked if there was a conflict of interest when Mrs Lee Suet Fern helped prepare it since her husband Hsien Yang stood to gain from the removal of his sister Wei Ling's extra share in the last will.

The last will also "differed in significant aspects from the first will", PM Lee noted in his statutory declaration to a ministerial committee, a summary of which was issued on Thursday.

The last will did not have a gift-over clause, and PM Lee said "there is nothing which suggests that Mr Lee had given instructions for it to be removed". This clause had provisions for shares of the late Mr Lee's estate to go directly to his grandchildren, if his sons died before him.

On the absence of this clause, Mr Lee Hsien Yang said based on instructions from his father for the last will to revert to the first, "We took what we understood to be the final version of the 2011 will, without realising that a gift-over clause had been in the executed version of the 2011 will. This was then engrossed without amendment."

Mr Lee Hsien Yang has also said his wife's firm Stamford Law Corporation - now known as Morgan Lewis Stamford LLC - did not draft any of his father's wills.

"The will was drafted by Kwa Kim Li of Lee & Lee," he said, referring to the sequence of events surrounding the final will.

Ms Kwa is his cousin and managing partner at Lee & Lee, the firm his parents had co-founded.

On Friday, Ms Kwa refuted Mr Lee Hsien Yang's claims. She told The Straits Times: "I did not prepare the last will."

PM Lee had also questioned why a clause, in which his father stated that he wanted his house demolished after his death, was re-inserted in the last will when it had been removed from the fifth and sixth versions of the will.

It is unclear why the late Mr Lee had changed his mind on the clause between the different versions of the will.

PM Lee also said "there is no evidence that Mr Lee even knew that the demolition clause had been re-inserted into the last will".

On Dec 17, 2013, the late Mr Lee had signed the final will in the presence of two lawyers from Mrs Lee Suet Fern's law firm. PM Lee had noted that the two lawyers, Mr Bernard Lui and Ms Elizabeth Kong, were present at his father's house for "15 minutes only, including the time for logging into and out from the property".

"They plainly came only to witness Mr Lee signing the last will and not to advise him," he said.

In his post, Mr Lee Hsien Yang produced excerpts of an e-mail that his sister, Dr Lee Wei Ling, wrote to him on Dec 16, 2013. The subject header of the e-mail was "Papa says to go back to 2011 will".

Dr Lee wrote: "To get a notary public not from Lee n Lee to witness his signature n (sic) that settles it."

Mr Lee Hsien Yang said the two lawyers - Mr Lui and Ms Kong - were called on to witness the signing of the will as Ms Kwa was not contactable.

"Lee Kuan Yew had read the final will carefully and initialled every page, including just below the demolition clause," he said, adding that the final will was subsequently given to Ms Kwa for safe-keeping.

In a later post on Saturday afternoon, Mr Lee Hsien Yang wrote: "The line spacing (of the will) was not dense. It was a four-page document he had seen before and was familiar with," he said.

He also cited a file note by the two lawyers, who witnessed the will signing at 11.10am.

The lawyers had noted that "LKY read through every line of the will and was comfortable to sign and initial at every page, which he did in our presence", Mr Lee Hsien Yang added.

He also reiterated that the proper venue to challenge a will is in court.

He noted that once probate is granted - which means a will recognised as final and legally binding - the hurdle to challenge a will is considerably higher.

PM Lee had said he did not challenge the validity of the last will in court as he wanted to "avoid a public fight which would tarnish the name and reputation of Mr Lee and the family".

To this, Mr Lee Hsien Yang said probate hearings can be heard "in camera", or behind closed doors.