In several cases, the Supreme Court has declared that the provisions of the will of the decedent must be followed and respected. However, an heir can ultimately (although indirectly) vary the disposition of the testator by disposing his share in the estate even prior to actual distribution. He can convey his eventual share for a greater or lesser value or exchange it for a different property, e.g. cash for property.
Any agreement that merely conveys an individual’s share in the estate is valid so long as such agreement was executed after the death of the decedent. Upon death, rights to the properties and rights to the estate are transferred to the heir. There is no legal bar for the heir to dispose of her hereditary share even if such disposition technically changes the distribution of the testator. (Mison)
