We're facing this situation as my aunt is dragging her heels about making a new will.
My brother (former solicitor, not family law) is predicting a shit show.
We're in Scotland. He thought it might be easier in England as we were all executors for the people (now dead) she appointed as executors in her 1980s will.
She and my Uncle actually went and did power of attorney documentation fairly recently as his dementia was incoming but she is such an admin disaster she declined to re-do the wills at that point. She didn't tell us they'd only done PoA
In case this sounds over invested stuff like this has been discussed in our close family a lot as everyone in the generation above her and her generation has died in the past 7 years. As a family we've done a lot of death. Some estates were much easier than others due to decent forward planning. She knows all this.
My father, now deceased, knowing what she was like specifically spoke to her about it before he died as he knew we would be landed with her affairs as he wasn't going to be around (she doesn't have kids).
Therefore it was something of a surprise when we discovered about six months ago that my Uncle's will is from the 1980s, and then she dropped the bombshell that hers is too and they didn't think it was important to update them despite our lovely family solicitor advising her when they did PoA that they should. My sister wasn't even born when her will was made. We've told my aunt we don't care if she leaves it all to the donkey sanctuary but would really appreciate if she makes a new will as it will save us a lot of hassle.
Despite all this she hasn't done us despite making my brother email her his list of family law recommendations about six times as lovely (endlessly patient) family solicitor has now retired. ARRRRGGGHHHHH.