Fionnuala McGoldrick was born in Marianville Mother and Baby Home in the south of the city, as was her older brother Paul, after her young unwed mother was sent there.
Paul died in another home from pneumonia seven months after he was born in August 1972.
Fionnuala, who was adopted into a new family, began the search to find her brother four years ago and a fortnight ago she obtained records that confirmed he was buried at the Bog Meadows on the edge of Milltown Cemetery in west Belfast.
The mass grave is believed to be the final resting place for so-called 'limbo babies' - unbaptised children denied a Christian burial.
"I feel that it was wrong to treat grieving parents like that anyway, but Paul was baptised and he had every right to be given a Christian burial on consecrated ground but that didn't happen. He was put in the ground with strangers without so much as a prayer," she told UTV.
"Countless other nameless, faceless babies who are in there that, for whatever reason, didn't have anybody to claim them at the time, whether that be because they were forcibly taken from their mothers or because they just didn't have anybody to the claim them.
"Human life is important and should be respected and it's terrible to think that 40 odd years ago, mass graves existed and that people had such little respect for human life that babies were treated in this way."
Her family has now been able to erect a cross marking where Paul is buried.
I feel that I am doing what wasn't done at the time for him, I'm actually acknowledging that his life was important, I'm acknowledging that he did exist and he did deserve to be recognised.
Fionnuala McGoldrick, whose brother was buried in a mass grave
Historian Toni Maguire has a personal connection with the cemetery as her uncle is buried in a mass grave there.
She quoted her mother speaking about him: "My little brother was buried in a mass grave in Milltown with 73 other babies in 1935, I am almost 90 years old now and it would be my most ardent wish to see baby Edward's name written in stone, instead of lying in a way that suggests my parents were ashamed of him."
She said approximately 11,000 individuals, including adults, children and infants, are buried in mass graves at the cemetery, but the true number will most likely never be determined.
"Because these graves were open graves, there were very insecure covering on them in the night-time. I think it's something you would find any poor ground, where you would have had graves open for months or sometimes even years," she explained.
"It was the tradition, it was what was done, these children, unbaptised babies could not be buried on consecrated ground and they were outside the remit of care of the Catholic Church in particular, but this is something that affects all the Christian religions in Northern Ireland. We have instances where we have poor ground burials, unmarked sites with mass graves like this all across the province."
Whenever the story broke about the scale of events in Tuam at the Bon Secours convent, obviously the alarm bells rang everywhere as to whether or not we could be facing a similar situation in our jurisdiction.
Deputy First Minister Martin McGuinness
In the Republic of Ireland, a state inquiry has been launched after the scandal in Tuam, Co Galway, recently came to light.
It was discovered that almost 800 babies and toddlers died between 1925 and 1961 at St Mary's Orphanage, which was run by the Bon Secours order of Catholic nuns. They are believed to be buried at a mass unmarked grave within the home's grounds, which was discovered in 1975 - but thought at the time to be a famine grave.
Ms Maguire has said there could be hundreds of sites across the island of Ireland where similar burials have been carried out.
She stressed the need for the truth for those who still do not know what happened to their loved ones.
"It was a heinous thing to treat children and individuals in this way, and it was really a big issue for those family members who still survived and have gone on for decades in some circumstances, looking for information on these children," she said.
"There are people still alive today suffering really badly, suffering a lot of pain and heartache. It sort of originates from a sense of shame, a sense of guilt sometimes, that their babies were treated in this way and sometimes the parents can feel 'it was my job to see that my child was buried' but they should not have this sense of guilt, the guilt is not theirs."
She continued: "We need to recognise the [burial] sites, we need to survey them, we need to see how far they extend because this has implications, and there have been a number of sites I've gone to see, and when I get there the site is gone and a development is on top of it.
"This is part of the issue, this anonymity for these sites within the landscape, we can't let that continue."
On Wednesday, deputy First Martin McGuinness will meet with campaigners calling for a similar probe to determine whether Northern Ireland children suffered the same fate.
He did say that "even at this early stage", there could be no doubt that children were most likely trafficked north and south of the border to different institutions.
"You can't rule out the probability that, yes, in the course of the recent history that children who were born in the north could have found themselves in the south and similarly, children who were born in the south in some of these homes could have found themselves north of the border," Mr McGuinness stated.
"I asked our officials to make a check on the number of mother and baby homes and where in the north and to carry out further investigations as to whether or not a similar situation existed here.
"There is no evidence that that's the case at the moment but it's still early days. In this jurisdiction we have a duty and a responsibility to carry out an exhaustive inquiry to ensure that we don't have a similar situation here."
Mr McGuinness stressed that if evidence was found, he would urge the Executive to back a similar inquiry as in the Republic.