There are so many cases where one sibling has manipulated an elderly parent to hand over POA, and have then proceeded to take control of all monies, property etc. This is especially common when early dementia is involved, as it is hard to prove mental competence at the time POA is granted.
When the elderly parent eventually passes away, any inheritance which was intended to be divided between all siblings, has already been disposed of.
The Court of Protection fails dismally in it's duty to protect the vulnerable.