You should change your title to read:
"How do beneficiaries establish their entitlement to inherit"!
The first thing a solicitor will ask when one of the beneficiaries comes in is to produce the title deeds - showing the person whsoe name is on the deeds, however long ago.
The next thing is to draw the family tree - where did we start and where are we now?
Then - tick off each applicable event that would affect ownership, look for evidence by way of death certificates, marriage certificates, etc.,etc. Some families, while crap at dealing with big events, are surprisingly good at the little detail and will be able to produce what is necessary - once they get the big picture.
Then seek whatever else is necessary and prepare an indication of likely cost. It may be necessary to seek a number of Grants of Probate/Administration to establish entitlement.
In the end, the aim of the beneficiaries should be to establish title such as would enable them to sell , if ever they want to.
It can be quite tedious - especially with clients who want a particular result which does not accord with the advice they are being given!
mf