If you don't get your inheritance, and you're a retainer, you can go to court with a custody suit. Who's entitled to a retainer? According to Article 991 the civil code, which is entitled to receive custody, are the descendents, the spouse and the parents of the heir.
The amount of support due to the rightholder shall be calculated as follows: If he is permanently unable to work, or if the downstream minor is entitled, he shall be entitled two third the value of the inheritance. In other cases, half of this share is due.
Court competent to file a lawsuit: according to Article 39 Code of Civil Procedure, the maintenance suit is brought before the court according to the last residence of the heir.