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Do beneficiaries of a will have rights?
Yes. The beneficiary(ies) as stipulated in a will have many and various rights.
With regards to the process of estate administration, a beneficiary may enquire of an executor or directly from the pffice of the Master of the High Court as to the progress of the winding up the estate.
With regards to inheritance, a beneficiary may renounce an inheritance. However, when they do so, they renounce their entire inheritance. They cannot renounce just one item or aspect of it.
When joint assets are bequeathed to two or more beneficiaries, the onus is generally on the beneficiaries to distribute the relevant assets amicably and in equal share or value.
If your query is more specific than this, it is a good idea to speak to a testamentary specialist.
(For the purposes of this answer, the term beneficiary(ies) refers to heir(s) and legatee(s) as well as the beneficiary(ies) of a trust.)