Is this normal?

[Todayisanewday75]

I fantasise about ending my relationship. I plan out all the practicalities in my mind. But in real life I can’t do it. Our lives are so intertwined and although eldest DC (not his) would love it younger two DC would be devastated, youngest has told me it’s her worst nightmare. I feel so stuck

The youngest two would get over it.
How long do you feel you should stay for their sake? I think watching their mum spending her life so unhappy would do more harm in the long run. Would you want them to learn that settling, and staying stuck, is what you have to do in life? Why does your eldest have to be the one to have their feelings disregarded for the sake of their siblings. No one wants their parents to split up, mine did at a time when it wasn’t very common, I was the only kid in my class with divorced parents, life goes on.
Leave op & be happy

Thanks @Igotchills I know you’re right but it just feels so hard

These children are not the arbiter of your relationship with your husband, you are.

And what Igotchills wrote.

The younger two will not be devastated. I'm afraid that's probably just what you're telling yourself to procrastinate from doing what you need to do.