Sibling conflict in adulthood is rarely about the estate. It is about which of you was believed, favoured or overlooked, and an inheritance is simply the first thing since childhood that can be counted.
The sibling relationship is the longest most people have, longer than a marriage and longer than a parent. It is also the one nobody chose, and the only one where the roles were assigned before anybody could object.
What brings people
A parent's illness and the unequal share of the caring. A will, and what it appeared to say about who mattered. A falling out at a funeral. Years of not speaking, and a wish to try again without knowing how to start.
How it is worked with
Sometimes siblings come together. More often one person comes alone, because the other will not, and that is workable. The aim is not always reconciliation. Sometimes it is deciding what contact you can live with, and stopping the argument from running in your head.
What a counsellor will not do
Adjudicate. Nobody in the room is going to be declared right about 1993.