The family of Clodagh Hawe faced debts of more than €50,000 in funeral and legal costs after her husband murdered her and their three sons.
Alan Hawe (40) killed Clodagh (39), Liam (13), Niall (11) and six-year-old Ryan before taking his own life in August 2016.
Clodagh's sister Jacqueline Connolly and mother Mary want the law changed so the estate of a murderer who has ended his or her own life cannot be passed on to their family.
Before he killed himself, Hawe, a deputy headteacher, withdrew large sums of money from the joint account he had with Clodagh and deposited it in his own account.
It is believed he did this so his family would inherit the money.
Jacqueline said that in the days and weeks after the killings in Co Cavan, Clodagh's family slowly started to learn that they had little in the way of rights.
This began when they moved to have Hawe's body exhumed from the grave he shared with Clodagh, Liam, Niall and Ryan at Castlerahan.
"When we tried to have the body exhumed we learnt, as we did on so many occasions, that we, Clodagh's next of kin, had no rights," said Jacqueline.
"It would be the Hawe family that would have the final say on whether there would or would not be an exhumation.
"We also would find out that under the Succession Act 1965, the Hawe family are entitled to all the proceeds of the estate.
"Mam and I had to quietly work alone to have the murderer removed from the family plot. It took over nine long months.
"To those of you who att-acked us on social media over our decision to bury the family together, all I can say is, if your intention was to wound us, you did, deeply, but we forgive you."
Last Thursday, Jacqueline and her mother met Justice Minister Charlie Flanagan to discuss the Succession Act.
"It must be reformed as soon as possible so that murderers, or their family if they end their own life, do not financially benefit from their crime," said Jacqueline.
"Let's get this law changed immediately. It won't be retrospective, so it won't solve our problem.
"Please, please stop financially rewarding the perpetrators of femicide and familicide.
"At the inquest, we learnt that after murdering Clodagh and before murdering the boys, Alan Hawe transferred funds and arranged his affairs so his family would be the sole financial beneficiaries of his estate.
"Please do not add insult to our injury, loss and grieving by thinking we want money."
Jacqueline said funeral and legal costs for the inquest have added up to more than €50,000.
"These are bills that my mother, who is retired, and I, a widow, are struggling to pay," she said.
Since the inquest, Clodagh's family have learnt that Hawe had been looking at porno- graphy on his school laptop and was experimenting with cross-dressing.
Jacqueline and her mother have been told by a local man that he saw Hawe driving very close to the school, where he was deputy head, on the morning of August 29.
"So, after he murdered his wife and three young sons, did he leave the house to go to his place of work, Castlerahan National School, where he was vice-principal, perhaps to destroy evidence?" Jacqueline asked in an interview with the Sunday Independent.
"When we asked a detective whether gardai pursued this line of inquiry - local witnesses saying they sighted the murderer driving that morning - we were accused of interfering with a witness because we allowed him to tell us what they saw that morning."