Parents Simon and Diane Pitcher are demanding a personal apology from the health service who sent a letter addressed to their dead son.
Ryan Pitcher died 15 years ago on Monday, aged three.
He was sent the standard letter as part of a campaign to encourage screening for a sexually transmitted disease by the Leicestershire Partnership NHS Trust, two days before the anniversary of his death.
The trust, which has launched a review, has admitted it may have sent out nine other letters to the families of dead youngsters.
Mr Pitcher said: "Sending out this letter was deeply insensitive and should never have happened.
"Every day we remember Ryan and we received this letter on Saturday, two days before the anniversary of when he died.
"It is just another issue with the health service. We were naturally deeply upset and my wife Diane left a message on the answer phone at the number on the bottom of the letter, expressing our shock."
Ryan was among 688 children misdiagnosed with epilepsy and given the wrong treatment by Dr Andrew Holton, then a paediatric neurologist at Leicester Royal Infirmary.
In 2009, the University Hospitals of Leicester NHS Trust admitted liability for Ryan's death and paid the family an undisclosed amount of compensation.
A report funded by the trust said one of the cocktail of drugs Ryan was given indirectly led to his death.
The letter, which arrived last Saturday, was one of 1,035 sent to young people in North West Leicestershire by the trust's families, young people and children's services department.
It was part of a pilot campaign to boost the number of people aged 15 to 24 being tested for the sexually transmitted disease chlamydia.
Mr Pitcher, 47, who lives in Heather, said: "We want an apology from the partnership trust and an undertaking that no-one else in the future will have to suffer as we have.
"However, I understand that up to nine other families could be in the same position as us.
"We could possibly understand the mistake occurring if Ryan's death had happened recently, but it is 15 years."
He said since leaving the message they had not been contacted by the Leicestershire Partnership NHS Trust.
He said: "We want them to acknowledge their mistake and say what is being doing to prevent it happening again."
A spokesman for the Trust said: "We would like express our sincere apologies for the distress this has caused the Pitcher family and we will be contacting the family to offer our apologies directly.
"Our aim in sending these letters was a genuine attempt to ensure as many young people as possible are protected against the serious effects of chlamydia.
"The patient information was correctly maintained on our systems and Ryan was marked as deceased on our records, so no correspondence should have been sent to his family."
He said a review was instigated immediately to determine how it happened.
The trust had identified a further nine families with deceased children who may have been sent the letter in error.
The spokesman said: "If they have, we will be contacting the families individually as soon as possible to apologise."
