Declaratory suit for unregistered fake will maintainable or not?

A childless widow is facing the issue of a fake will from her husband side of the family. They falsely claim that her husband has written an unregistered will giving her life estate to two properties, a house and a commercial shop property and after her life time these two properties are to be given to two legal heirs of her husband side of the family. The husband side of the family was renting the commercial shop property but they stopped paying rent during the Covid lockdown, closed their business and sub-rented the shop property to another business and enjoying the rent. One year after the death of her husband the husband side of her family filed a declaratory suit in the District Principal Munsif Court to declare the will as valid along with few other reliefs such as permanent injunction against alienating and disturbing suit properties. The suit is based completely on false facts and fake will and they are using the legal system as a weapon to harass the helpless widow for enjoying her property. One of the beneficiaries of the will is a practicing advocate so the will seems to meet all legal requirements. No executor is named in the will though two beneficiaries are named. Is the declaratory suit maintainable in this situation or a petition for Letter of Administration (LoA) has to be filed in the District Court which may become a Testamentary Suit once the defendant files objection?