A contract to make a will or devise, or not to revoke a will or devise, or to die intestate, if executed after January 1, 1997, may be established only by:
(1) Provisions of a will stating material provisions of the contract;
(2) An express reference in a will to a contract and extrinsic evidence proving the terms of the contract; or
(3) A writing evidencing the contract and signed by the party alleged to have breached the contract.
The execution of a joint will or mutual wills shall not create a presumption of a contract not to revoke the will or wills.