Morbid question I know, but…How do the police know whose door to knock on if something happens to you?

[Hermanfromguesswho]

Inspired by another thread asking what people would assume if police officers knocked on your door and the overwhelming response was to worry that something had happened to a loved one.
Anyone who works in the police…how do you know who is next of kin/emergency contact?
I, for example, am a single parent of teenagers. I live alone with them.
Their Dad lives a couple of hours away. I have parents and siblings, who I am in close contact with but they all live at least 3 hours away and although they know what I do, they don’t know the name of where I work. They know my friends names but don’t have their contact details.
My whole support system here is a couple of very close friends (one is my children’s godparent) and my ex parent in laws (who live locally)
Morbid thought but I worry if I had a serious car accident and was badly injured or killed, how would my children find out? Is there somewhere I can register my friend and in laws as my official emergency contacts as they would be best placed to be with my children, care for them and inform the children’s Dad and my work etc.
I wouldn’t want someone knocking on my Mums door 3 hours away who would be lost and not know how to deal with it all!!

I assume they had to keep someone at the house to meet all the parents as they arrived to pick their kids up? Notice sounds like a rarely needed but important contingency, and not something I would have thought of!

I had a very sad situation at work where the police turned up looking for one of our young employees whose parents had been killed in an accident. They had identified them and then went to their house (not sure how they got in) and found his payslip in his room and tracked him to our workplace. That was a bloody awful day. 😢

When my sister died, the man who found her (a neighbour) said he was her partner and NoK. This was believed and meant my parents never had the police arrive to tell them, so we also never had a Police Liaison Officer to guide us. The inquest was so delayed that I only saw his statement over a year later and just three days before the inquest. It was misleading at best, lies at worst. He wasn’t at the inquest, nobody else identified my sister so I’ll never know. He now has my nephew and there’s nothing we can do.