Succession clauses in antenuptial contracts
Agreements relating to inheritance are unenforceable. There is however one exception to the rule. Succession clauses can be included in an antenuptial contract. Each spouse can be party hereto, and third parties may also be a party hereto. The parties can declare that, upon the death of either spouse, the survivor shall be entitled to the entire estate.
I would not advise including agreements relating to an inheritance in an antenuptial contract. The stipulation is binding to the one party without the consent of the beneficiary even if there is a subsequent will in place. The parties may therefore amend or cancel such stipulations in the antenuptial contract by making a new will, but the surviving beneficiary will still be able to choose between the provision in the joint will or the provision in the antenuptial contract.
Third persons can also be named as heirs. Such a provision cannot be cancelled in a subsequent will without the consent of the benefiting party, on condition that the beneficiary is also a party to the antenuptial contract.
The agreement in an antenuptial contract therefore limits a party should they want to change the provisions with a later will.
There was one case (Ex Parte Joannou) where a full bench allowed the deletion of a pactum successorium entered into by the spouses. They were advised by an attorney that the provision in the antenuptial contract can be revoked at any time. The decision was based on the grounds that the spouses acted in ignorance of their rights and that the antenuptial contract did not give effect to their true agreement.