If the adopted is a minor or otherwise incapacitated, the adoption may be judicially rescinded upon petition of any person authorized by the court or proper government instrumental acting on his behalf, on the same grounds prescribed for loss or suspension of parental authority. If the adopted is at least eighteen years of age, he may petition for judicial rescission of the adoption on the same grounds prescribed for disinheriting an ascendant. (40a, PD 603)