Article and interview by ITV Calendar Correspondent Emma Wilkinson
Every day the family of Bethany Vincent and her young son Darren Henson live with the pain of knowing they will never see them, never hold them again.
The cruel way in which their lives were cut short by Bethany's violent ex-partner has saddened and outraged people across the country, but Bethany's parents do not want to spend time thinking about him.
Caroline and Darren Vincent want to focus on their "beautiful, kind" eldest daughter - a young woman who doted on her two sons; loved reading books and enjoyed getting out for coffee with her mum and sister.
They want to focus on their eldest grandson, DJ, their "special boy" - a nine-year-old who was gentle and clever and got so much joy from his beloved Chelsea F.C.
They want to make sure that their legacy lives on and they hope that through sharing their experience, other families might not have to go through the indescribable pain that they have.
"We'll never get Bethany and DJ back," said Bethany's dad, "but I think there are things that people can take away from what's happened to us, things they might relate to, that might help make a difference in the future."
"After we lost them, some lovely people in Louth created a new charity in their memory called 'Be Their Voice'. We, and DJ's father Kieran, are fully behind it and it sums up exactly what we intend to do - be their voice and try to help others."
Through 'Be Their Voice', the family want to help raise awareness of the early signs of toxic and abusive behaviour in relationships.
They were not aware of the extent of Boulton's criminal history when he began dating their daughter and while the relationship seemed fine at first, they soon started to see some worrying signs of control and manipulation.
Caroline said: "He encouraged her to give up her job, which she loved, by telling her she could do better. We had always been really close but he gradually isolated her from us and she stopped coming round as much.
"We tried to tell her it wasn't right, but it was like she was brainwashed and the more we pushed, the more she swayed towards him. It was all about control, and we just want other people to look out for signs like that."
Darren and Caroline hope that a new charity will support other people in Bethany's position
Bethany did leave the relationship at the beginning of last year, and her family felt like they had finally got the daughter they knew back.
Her parents still have many questions about how it was possible for a man with such a long, violent history to be able to do what he did.
Caroline Vincent said: "For someone with a history like his to still be able to roam the streets and keep getting away with a slap on the wrist is just wrong.
"I'm not saying I blame anyone else for what happened, but we do believe there were some failings.
"Every department had details of him on their files so I think communication needs to be so much better within the whole system to try to stop things like this happening."
"He was on the radar" - Bethany's parents want answers about why Boulton was able to do what he did
Last May Daniel Boulton walked 28 miles from Skegness to Louth, broke into Bethany's home and stabbed her and DJ multiple times.
During his trial it was revealed that he had a string of previous convictions for violence. They included assaulting police officers, attacking a former girlfriend, hitting someone over the head with a bottle and demanding a man hand over his phone at knifepoint.
He was also convicted of assaults on Bethany and was twice ordered by the court not to contact her. At the time of the murders, a restraining order was still in place.
A joint child safeguarding practice and domestic homicide review in relation to this case is underway and is due to be published later this year. The Vincent family hope it will provide them with more answers.
Caroline last spoke to Bethany and DJ shortly before they died - DJ was looking forward to going to bed in his Chelsea shirt and Bethany was excited to be moving house a few days later.
That is how the family want to remember them - happy and hopeful. And, they say, they will do all they can to ensure that Bethany's surviving son grows up being proud of the legacy his mum and brother have left behind.
Bethany's sister, Chloe, said she knows Bethany and DJ would be proud of what the family are doing in their memory.
"We can be the voice that they can't be," she said, "and we really hope to raise awareness of domestic abuse as much as we can."
Local volunteers at the charity are now planning a number of events and hope to soon begin working with young people to promote healthy relationships.
Caroline said while they will never get Bethany and DJ back, they do not want anyone else to go through what they have: "If one person reads our story and they leave an abusive relationship, report abuse, or reach out for help, then that will bring us all some comfort."
If you or someone you know is in danger, dial 999.
Domestic abuse helplines:
Refuge helps clients rebuild their lives and overcome many different forms of violence and abuse - including domestic violence, sexual violence, so-called ‘honour’-based violence, human trafficking and modern slavery, and female genital mutilation.
Telephone: 0808 2000 247
Women’s Aid is the national charity working to end domestic abuse against women and children.
Email: email@example.com Online live chat: https://chat.womensaid.org.uk
Men's Advice Line
Men's Advice Line seeks to increase the safety of men experiencing domestic abuse, and the safety of any children, by providing confidential support.
Telephone 0808 8010 327
Be Their Voice
The charity was set up in the wake of Bethany and DJ's deaths by people in Louth. They are promoting education surrounding domestic abuse in Lincolnshire.