The United Kingdom is, as so often, again an exception in Europe. Most European states follow the Code Napoléon: the children have an automatic right to a part of the Estate, even if they are not expressly mentioned in a Testament. It is not allowed to make fideï commissionary regulations (benefitting one heir at the cost of other heirs with an equal grade of consanguity). In the UK a Peer can settle that the whole ancestral estate goes to the eldest son and successor to the Peerage. On the Continent this is very diffficult, this is also an answer why in the UK many Peers still have large estates in comparison to their counterparts on the Continent.
Of course there are legal solutions, like the placement of an estate into a juridical vehicle, like a family foundation. Such a foundation can not die and is therefore not subjected to inheritance taxes. The statues of such a foundation can precisely describe the intentions, arrangements and workings for the benefit of specific named persons. For an example: "the properties placed into the foundation are given at the disposal of the Bearer of the Crown and are subservient to the execution of the royal dignity. The properties placed into the Foundation can not be estranged or sold."
