Proof of kinship may be needed when accepting an inheritance by law (if there is a will, then such problems will not arise, since such inheritance is not limited to the framework of kinship).
collection of the necessary documents
If you are faced with the need to prove your relationship with the testator, then personally contact the registry office for confirmation or send a request from a notary. If you cannot obtain the necessary documents or if they are insufficient to prove the relationship (also if they do not prove it at all), file a lawsuit to establish the fact of relationship. Next, it will be decided what other documents you must provide. Demand them with a court request to the right authorities.
Note that it is not easy to prove family relationships and that it can take a considerable amount of time (from a couple of months to several years). As evidence, you can submit any information to the court, be it documents from the registry office, telegrams, letters, photographs, video recordings and much more. By the way, documents serving only as indirect proof of kinship must be provided in the aggregate.
Here is a list of documents that can confirm your relationship with the testator: marks in the passport about children and spouse, certificates of kinship issued by the organization at the place of residence or work of the heirs, as well as the testators themselves. Extracts from house books, testimonies, receipts, audio recordings, and even checks will do. You can prove the relationship thanks to a document that indicates that you are disabled and were dependent on the testator for at least a year before the opening of the inheritance.