I think whether you can sleep at night with whatever decision you make really depends on the reasons why the relationship breaks down.
My sociopath sibling treated our father like crap for decades, NC for long periods of time without even telling anyone why, expected everyone else to play go-between because they still wanted a link back... the reasons for which became obvious when DF died and suddenly she was very interested in his life and money. He did, in fact, leave everything equally amongst his children and had never had any intention of doing otherwise.
The sibling has treated our stepmother even worse over the years, alternating between deliberately ignoring her and mocking her behind her back, saying spiteful things to and about someone who had done absolutely nothing to deserve it. When DF died they started out playing happy families with DSM, but it became obvious very quickly this was only for what stepmum might be useful for.
DF also left DSM a good six figure sum to look after herself, with the wish expressed that it come back to his children if not required/spent. Well, when DSM shuffles off my sibling is going to get a nasty shock as our father's money, if any is left, will skip a generation and go straight to the grandchildren instead, which means sociopath sibling's family gets rather less than their 'fair' share. To add insult to injury, as the grandchildren are all very young the Will asks me to be Trustee and explicitly forbids my sibling benefiting from it.
The final act in all of this is that DSM - who has no family of her own - is actually quite wealthy herself anyway, which my sibling does not know and has made some very objectionable assumptions about. There's an even bigger surprise coming there!
It's going to be extremely divisive, but my relationship with this sibling is extremely strained already and it may well not last until then anyway. I've talked about it extensively with DSM and fully support her stance.