Survivors of the Protestant-run Bethany mother and baby home have added the names of 70 children and a mother to their memorial to Bethany children in Dublin's Mount Jerome Cemetery.
All the individuals concerned were buried in unmarked graves between 1922 and the late 1950s.
The names of 169 more Protestant children, mainly from Church of Ireland institutions have been inscribed on a separate upright memorial stone nearby which was also unveiled this afternoon.
The unveiling took place after a service at the cemetery entitled "For the Little Ones - Remembrance 2018".
The Bethany Home Survivors' Group ‘98 said research conducted on its behalf has found that the group of 169 children were resident in or under the care of Miss Smyly's Homes, Miss Carr's Home, the Church of Ireland Magdalen Asylum and the Irish Church Missions.
It said many of the children were 'nursed out' by the institutions and died under the care of foster mothers, who were paid by local authorities.
In 2010 the group first revealed the names of 219 dead Bethany children. The original Bethany memorial stone, bearing 222 names, was unveiled in Mount Jerome in April 2014.
At today's ceremony a white dove was released. Warwickshire-based Derek Leinster who was born in Bethany in 1941 said this was "to remember the little ones that lost their lives in the Bethany Home".
The Group said the memorials mark the death of hundreds of children who were under the care of the Protestant evangelical institution which moved from Dublin's north inner city to Rathgar in the 1930s.
"There is no room on our current memorial for new Bethany Home children", said Mr Leinster who explained that the group commissioned a new flat stone which is laid at right angles to it at its base.
Mr Leinster added: "In addition to the Church of Ireland, the Presbyterian and Methodist churches also supported the Bethany Home and other institutions.
"They sent women and children to them, not only from the Republic but also from Northern Ireland. The Presbyterians and Methodists also need to be held to account."
He said that for the first time the Bethany stone also recognises the mothers of the home. This follows the group's discovery of two Bethany Home mothers who died in childbirth. One of the mothers is named on the stone.
"It is understood that she died in childbirth of blood loss, and that, tragically, her child died five weeks afterwards," Mr Leinster explained.
"I thought it was fitting to have her looking after all of these little ones," said Leinster.
"I knew there had been mothers who died in the Bethany Home but we had never been able to identify any before now," he said.
He added: "This sad time will allow us to reflect on all of the Irish children that suffered abuse while in the care of churches and the State.
"It is important that we do this while we can because, as time goes by, there are fewer of us able to attend."
For 20 years, the Bethany Home survivors have campaigned without success for redress payments from the State.
Sinn Féin leader Mary Lou McDonald, speaking at the unveiling, criticised successive Governments for failing to compensate survivors of the Bethany mother and baby home and similar Protestant-run institutions.