It does not matter what happened 50 years ago. If you purchased in good faith, based on the information then recorded at the Registrar of Titles, you will be OK. I'm copying below two paragraphs from an article I recently pubished:
"Since 1920, the Dominican Republic has employed the Torrens system for real estate registration purposes. This system was developed in Australia in the 19th century and is now widely used in many countries. In the Torrens title system, a register of land holdings is maintained by the government, which guarantees an indefeasible title to the properties included in the register. Land ownership is transferred through registration of title instead of using deeds. The registrar has a duty to ensure that only legally valid changes are made to the register. Any interest affecting or limiting the ownership rights of the registered owner, such as mortgages, easements, liens, etc., must also be registered. Interest in real estate (property, mortgages, privileges, etc.) is only valid and enforceable against third parties upon registration at the office where the register is located (called ‘Registry of Titles’ in the Dominican Republic). Once registered, the system guarantees title and priority on a first come, first served basis.
In the Torrens system a third party, acting in good faith, can rely on the information in the land register as to the ownership of a property and the other rights and interests that may affect it. In a property purchase, the buyer is not required to look beyond the record in the register. In contrast, in the common law system a vendor cannot transfer to a purchaser a greater interest than he or she owns, and the seller’s title is as good or as defective as the weakest link in the chain of title, which necessitates a chain-of-title investigation at the record office".
Of course, the above does not mean that you can prevent somebody from suing you on preposterous grounds. However, the case won't go anywhere.