EJ....sabau has some very wise thoughts on delayed grief and reasons for...it may fit your situation or it may not.
grieving can be so individual in how it surfaces, resurfaces, gets worked on, gets worked through, arises yet again.....and so on....
the 33 years you've survived and the 26 years for sabau both resonate in our life as we've spent more than a quarter decade w/o a parent.
loss is loss. when the loss happens and how the loss is dealt with at that time can indicate how it will be further down the road....sometimes.....and like you're finding out now there still remains some unfinished grieving to do.
very sorry for the loss of your brother and so suddenly as well.
glad that you're writing about it here. grieving doesn't need to be a mysterious hidden process. the more shared, sometimes, the easier the burden and the less alone one can feel.
you're not alone......your subject line hits home with many.