Report by ITV Granada Reports correspondent Mel Barham
A mother whose three-year-old died suddenly on Boxing Day has discovered he suffered from a rare genetic disorder - which her daughter has now been diagnosed with as well.
Alexander Cooper suffered a cardiac arrest in 2021 with no obvious symptoms or indication he was ill.
After two years without answers the family finally discovered his death was caused by a rare genetic mutation - and mum Emily Cooper now has to carry a defibrillator around with her in case her 20-month-old daughter suffers the same fate.
Dr Emily, from Lancaster, said: "At first I was elated... After all this time there's something to explain what happened to our lovely boy.
"The gene mutation - you sort of naturally assume it's only something that would have happened to him.
"But as the call went on I realised it's actually a recessive inherited condition, and I realised that oh no, it was a recessive that the other children are at risk."
Alexander had woken with a mild stomach bug on Christmas Day 2021, but by Boxing Day lunch h e said he was feeling better - so Emily had taken his brother for a walk.
But when she returned home, she saw police cars outside of her home.
Dr Cooper said: "Somebody said Alexander had had a seizure... I got to the hospital and was told my husband had done a heroic job of CPR at home, on his own, they’d managed to get his heart going again, but they just couldn’t sustain it.
"I watched them withdraw CPR and he died."
Alexander had no obvious symptoms or previous indication that he was ill, which made his death all the more difficult for his family to process.
Emily said: "It was so horrendously abrupt, he was just so healthy and happy and energetic.
"It was so hard to get our head around, we just lived in disbelief, in trauma. It's hard to articulate how much it affected us, how much it affects us now."
After finding out about the rare genetic mutation the family were lucky to get access to whole genome sequencing tests which showed Alexander's brother Freddie and Emily's unborn daughter are unaffected.
But his 20-month-old sister Isabelle has inherited the same faulty gene.
Emily says the diagnosis is helpful as Isabelle now has a chance of surviving.
"Now she has a chance, we didn't get that with Alexander, although everything is still really unknown it gives me a little bit of hope, she could be one of the lucky ones who never gets affected."
She now carries around a defibrillator donated to her by the Oliver King Foundation.
The charity was set up by the family of 12-year-old Oliver from Liverpool who died of Sudden Arrhythmic Death Syndrome, a hidden heart condition which kills 12 young people every week.
"It gives us that extra security that if she does ever have a cardiac event that we have that security that follows her everywhere in her backpack," Emily says
Alexander's family want to raise awareness and for others to be given access to testing to avoid going through what they have.
Emily's family were able to get genetic tests after Alexander's death thanks to charity SUDC - Sudden Unexplained Death in Childhood.
Nikki Speed from the charity spoke to Granada Reports presenters Mike Hall and Ann O'Connor.