Different ountries have different laws about the drafting and proving of wills. The succession laws are not even uniform across Australia.
If you have assets in more than one country it is advisable that a will is drafted in each country. There are also practical reasons for having wills in each country.
If you have minor children it is very important that you appoint one or more guardians in your wills. You can appoint as guardians your relatives or friends in South Africa. You should firstly ensure that the guardians agree with their appointment.
If you fail to appoint a guardian in your wills the Court will choose a guardian from those who step forward. If no one does, the court will decide where your children will live, and who will make legal decisions for them.
In summary:
Trustees of discretionary trusts are bound to act on behalf of the broad discretionary beneficiary class and are bound to consider all the beneficiaries in exercising discretion to make distributions of income, capital and when investing moneys. A mere discretionary beneficiary, to the extent that they haven't been allocated any income/capital does not have any proprietary rights to income or capital of the trust. Those beneficiaries are mere discretionary beneficiaries and only have a right of due administration of the trust estate at law (ie they must be considered by the trustee when the trustee makes distributions). The trustee is generally not bound to give its reasons for the exercise of discretion, and can choose to make equal, unequal or no distributions to a particular beneficiary and wouldn't be seen to do anything wrong given the discretionary nature of the trust.
However, having said the above, the terms of the trust deed need to be examined by a lawyer in detail to confirm whether an aggrieved beneficiary has any other recourse. For instance, the terms of the trust may provide for an "appointor" who is the party (separate from the trustee), who is able to appoint and remove the trustee, thus having overall control.
Contact a lawyer to carefully review the terms oftrust for this purpose. Also contact the trust's accountant to get a copy of the latest balance sheetsshowing any unpaid present entitlements/loan accounts owing to particular beneficiaries.