Mason Djemat died in August 2017 at the Royal Hospital for Children in Glasgow, weeks before 10-year-old Milly Main.
He had been treated at one of the wards that were later closed following concerns over the water.
Kimberly Darroch has already said she is 100% certain the death of her daughter Milly, who was being treated for cancer, was linked to contaminated water.
• READ MORE: Jeane Freeman apologies for 'suffering and grief' of parents whose children died at infection-hit hospitalTwo wards at the Royal Hospital for Children (RHC) in Glasgow were closed last September and patients moved to the adjoining Queen Elizabeth University Hospital (QEUH), which is part of the same campus, as Health Protection Scotland (HPS) investigated water contamination incidents.
Health Secretary Jeane Freeman apologised to the families affected as she made a statement to MSPs on Wednesday.
Mason's mother, Victoria Freeman, said she is disappointed at the response from authorities, as she seeks answers over the death of the son she "absolutely adored".
She told BBC Scotland: "There was no-one listening to me. No-one wanted to help. No-one at all."
Ms Freeman said she first wrote to the health secretary last September and has been disappointed by the response.
She said: "I don't think that Mason was acknowledged, particularly by her, and I feel that she did not take Mason's death seriously."
• READ MORE: Hospital scandal parents receive apology from Jeane Freeman for ‘suffering and grief’She also said she got no response from the health board NHS Greater Glasgow and Clyde (NHSGGC), until she went to the hospital and demanded to speak to somebody.
When asked how she felt she had been treated, she told the BBC: "I don't think as a family we have been treated fairly."
Ms Freeman said her son had Hunter syndrome, a rare genetic condition, but was "extremely healthy" and strong when he was admitted to the hospital in the summer of 2017, and she was shocked when he suddenly died.
She said: "To be standing in ICU and thinking over in my head 'What's happened?' I just still don't have the answers and they don't have the answers as well."
She added: "Mason was the love of my life. Unfortunately I will never be able to replace him. Never.
"He was just really something. I absolutely adored him."
Health Secretary Jeane Freeman said: "I cannot begin to imagine the pain of losing a child in these circumstances - or the suffering and grief that will stay with them for the rest of their lives.
"My sincerest condolences go to Ms Freeman and the other families affected by this. I also want to assure you all that you will get answers and the support you need.
"Ms Freeman first contacted me about the death of her son in late 2018, and I responded. She wrote to me again at the start of this year and I replied, and this was followed by further correspondence just a few days ago.
"I'd like the opportunity to meet with Ms Freeman to listen to her views but also assure her, and the other families affected by this, that we are taking action."
An NHSGGC spokesman said: "We are very sorry Ms Freeman feels she has unanswered questions regarding the death of her son, Mason Djemat.
"The case was fully investigated and the outcome shared with the family.
"We met with Ms Freeman on a number of occasions to respond to any concerns she had and can confirm we remain in contact to answer any follow-up questions."