I understand that the idea of mortality is a hard thing to digest. I remember being terrified when I learnt about death, thinking it was imminent and I'd be left without parents and probably in some kind of Victorian orphanage. I was probably about the same age.
But my littlest one talks about it a lot. Cries and says "I don't want you to die ever" or I just suddenly see him with tears in his eyes and when I ask what's wrong, he says "I will miss everyone when they die." Or he says that he is afraid to die. He talks a lot about souls and whether there is a heaven etc. I think this was all prompted by the death of a pet and the realisation that they weren't coming back, the Pixar film 'Soul' and a lad in his class who plays by saying "I'll squeeze you to death and then you'll be gone!!" Plus the coronavirus- the little ones know that people were dying in overwhelming numbers thanks to a really poorly thought out assembly that the headteacher even included the infant school kids in.
This morning though, he said "I've made a plan. When you die and Daddy dies and my brother and sister die, I will go out to the busy road and lay down for a car to run me over so I can be with you all again. I will never be happy without you."
Is that extreme? Is that a regular thought process and typical of a problem-solution with five year old understanding? My older two never said things like this. They went through the usual sadness when they developed understanding of mortality, but it didn't linger so long or have such sad statements