A contract to make a will or devise, or not to revoke a will or devise, or to die intestate, if executed after September 1, 2019, can be established only by:
1. Material provisions. Provisions of a will stating material provisions of the contract;
2. Express reference, extrinsic evidence. An express reference in a will to a contract and extrinsic evidence proving the terms of the contract; or
3. Writing evidencing the contract. A writing signed by the decedent evidencing the contract.
The execution of a joint will or mutual wills does not create a presumption of a contract not to revoke the will or wills.