Tony Wotton, a paranoid schizophrenic, admitted manslaughter by diminished responsibility when he killed his 71-year-old father Terence in 2011.
Now an inquest is due to open at noon on Monday.
Mr Wotton's daughter Diane Ludlow and her husband Peter, along with Mr Wotton's sister Irene, attended a pre-inquest hearing at Gravesend's Old Town Hall back in May.
Speaking briefly, Mrs Ludlow said: "My dad had every right to life and the people have to answer why this happened and why it led to his death."
In June 2012, Tony Wotton had been charged with murder but the prosecution accepted the manslaughter charge.
Maidstone Crown Court heard how a crisis team, made up of mental health professionals and a doctor, saw Tony Wotton before the stabbing at his parents' home in Mackenzie Way, Gravesend.
In the days leading up to the killing, Tony's mother and Terence's wife Joan contacted his psychiatric nurse saying that her son had become irritable and aggressive.
The nurse visited and found he was also showing signs of paranoia.
A crisis team turned up, but Tony Wotton had left the house.
On the day of the attack, the crisis team visited again. They could find no grounds to re-admit him to hospital but told him that he needed to take his medication.
That evening, Tony Wotton stabbed his father in the back. Mr Wotton fell, pulling himself into the foetal position as the attack continued.
At the crown court in 2012, a mental health order was made keeping Tony Wotton in a medium security unit indefinitely.
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