Margaret Donohue, 35, from Lucan in west Dublin, believed her cousins and in-laws were having a gathering and may have fallen asleep before the inferno broke out at a halting site for travellers near Dublin on Saturday. They were the latest in a number of deaths to afflict the Connors and Lynch families.
Forensics officers combed the blackened remains of a prefabricated unit as they searched for clues. A child's buggy and chair sat abandoned in the middle of the yard.
Ms Donohue said: "It is horrendous, it is horrible for anybody."
The fire broke out in Carrickmines, south Dublin. A six-month-old baby was rescued from the flames by firefighters who risked their lives but later died in hospital. A child survived, Ms Donohue said, because he was not at the site.
The families lived at the encampment off the Glenamuck Road, just south of the M50 motorway and a few miles from Sandyford village, for about eight years.
The fire is being treated as a tragic accident, a traveller support group said.
Ms Donohue is a cousin of one of the families and an in-law of the other.
Thomas Connors, 28, his wife Sylvia, 25, and three of their children - Jim, Christy and six-month-old Mary - perished in the fire.
Another son, five-year-old Michael, was lucky to escape the blaze because he was staying with his grandparents nearby.
Sylvia's brother Willy Lynch, his partner Tara Gilbert and their children Jodie, eight, and four-year-old Kelsey were also killed.
The tenth victim is Jimmy Lynch, 39.
Ms Donohue said: "It is hard times, they only buried their own mother on New Year's Eve gone and their grandmother only just three months ago; for this to happen to just the one family is terrible.
"They have had it the whole year round, since the start of the new year, it has been tragic for the whole lot of them really, the whole family they are taking it really bad."
She said nobody was sure of the cause.
"We won't know until they are done doing their work."
She praised firefighters for their efforts to save lives.
"There was one lad who was an advance paramedic who went in and saved the young fella.
"He risked his life to save the young fella which I think was very, very good and heartwarming of him to do.
"It is sad for them to grow up with no parents, no mam and no dad. They have all the other family, they are enough for them, but your mam is your mam and your dad is your dad."
Clare Clifford, 32, from nearby Stepaside village added her bouquet to the bulging mass of flowers which dominated the entrance to the scene. Her own child was born six weeks ago.
"It is the loss of young life and there was a pregnant woman as well who died, I know what that is like, being pregnant, and it is very sad that her unborn child was lost as well," she said.
"I just wanted to express in some small way my sorrow at what has happened to this family, I had a bereavement in my own family a couple of months ago and I can only imagine what having 10 members of your family must be like, family and friends, it is unbelievable."
Appeals for support for the victims have been launched. Charity St Vincent De Paul is to seek contributions while traveller support networks have also sought funds.
Dun Laoghaire-Rathdown County Council has stepped in to help accommodate the rest of the residents of the halting site.
Taoiseach Enda Kenny also visited the scene on Sunday.