OP, I found myself wondering here about family history. My DM and her siblings managed to get through the death of their mother without arguing or fighting because they'd all felt equally loved growing up and the family as a whole was resilient. One sibling ended up doing the lion's share and did it willingly as she loved her Mum and was closest and had most time. My DM did the least as she was physically furthest away, but she did what she could and was not resented.
When my FIL died, my SIL ended up doing a lot of the work involved. It was done from a sense of duty, and if you understand the acronym FOG, well she was right in the middle of it. She stopped speaking to us and still isn't years later.
On one level, I can't really get my head around SIL's resentment as she chose to do way more than was strictly necessary.and resented us because we didn't do the same. For the record, we would have done way more, but were turned away from every suggestion by MIL who nursed a sense of martyrdom throughout.
The problem stemmed from insecurities that were set up years before the actual death. I get the impression from your posts that there may be a similar dynamic occurring within your family. Do you feel that there is imbalance between how you are all being pulled about?
I don't have any useful suggestions. I mostly feel sorry for SIL, because she's obviously unhappy on many levels to hold the levels of resentment that she has. I agree to an extent that you should perhaps, cut your brother some slack, but if you genuinely feel you have done what you can in a difficult situation, then cut yourself some slack too.
I don't feel any guilt over FIL's death and I am fairly sure my DH doesn't either. MIL continues to be upset that SIL and DH aren't speaking, but seems blind to the fact it was her who created the dynamic.
You may not be able to fix it, but do what you can. If your resentment of your brother's words is partly based in your own feelings of guilt, then you need to look at whether you are doing enough. Try to be compassionate with yourself and your brother. I hope you can find some common ground.