A 42-year-old woman has been charged with four counts of murder following a Denbighshire flat fire.
Lee-Anna Shiers, 20, her 15-month-old son Charlie, nephew Bailey Allen, four, and two-year-old niece Skye died after the blaze in Prestatyn on 19 October.
Melanie Jane Smith will appear at Prestatyn Magistrates' Court on Tuesday.
She is also accused of one count of arson with intent to endanger life and threats to commit criminal damage.
Karen Dixon, district crown prosecutor, said: "The Crown Prosecution Service has been working with North Wales Police as their investigation into the circumstances surrounding this tragic fire has developed.
"Our role at this stage is to review the evidence gathered so far by North Wales Police and issue advice in respect of criminal charges.
"I can confirm that, having carried out a detailed evidential review, our conclusion is that there is sufficient evidence to charge Melanie Jane Smith with four counts of murder, one count of arson with intent to endanger life and one count of threats to cause criminal damage.
Ms Dixon said it was in the public interest to charge Ms Smith with these offences.
She added: "With criminal proceedings now underway, I would like to stress the importance of maintaining both the integrity of the ongoing police investigation and the defendant's right to a fair trial.
"I would therefore ask that nothing is placed in the public domain that may undermine the criminal justice process."