A bit more information
My 2 brothers are the executors, one of which had power of attorney - he had been looking after mum's finances for a few months before her death.
A Power of Attorney typically expires upon the death of the Principal.
In the office of Power of Attorney Holder, he was accountable to her.
He was not accountable
in that office to any prospective beneficiaries.
Yes, in that office, he did indeed have a duty to generally preserve her money and assets,
and apply them to her interests (and perhaps, to recover reasonable costs he incurred personally in doing so).
But that duty was owed to her, not to any future beneficiaries.
Which means that, without either his consent, which he is free to withhold, without giving reasons,
or without making an accusation of misconduct of some sort,
of the kind that could give rise to things like Discovery Orders,
I do not see where you yourself have any general/automatic right
to merely "browse" that material, nor go on a fishing trip.
Truth be, unless you're an accountant, you may not understand it (in a way that has weight of law) anyway.
I am estranged from both brothers. The affidavit of executors listed my mum's cash assets about 50k, but mum had said she had approx. 120k.
I don't believe either of them did anything untoward, but I would like more insight into the discrepancy by having access to her financial information
With all due courtesy - stop pretending.
You want to know where the rest of the money is, or where it went.
Or indeed, if it ever existed (after all, Mum might have been mistaken).
Let me be clear - That's fair enough.
But, you are in the realm of death and money and greed and power.
I suggest that you will have a better time, if you are not naive about what you really think,
and about what you may have to do here.