Facts
Mrs. Businger was the owner of a real estate property in Horw. On May 14, 1956, her granddaughter Bernadette von Sury, acting as an authorized representative, sold this property to Gerold Kunz for a price of 600,000 francs. That same evening, Mrs. Businger passed away, leaving her two daughters, Mrs. von Sury and Mrs. von Moos, as her heirs.
In November 1956, Kunz filed an action with the District Court of Lucerne-Campagne against the two heirs to be awarded ownership of the sold real estate. Mrs. von Sury acknowledged the claim, but Mrs. von Moos contested the territorial jurisdiction of the court. This objection was upheld, on appeal, by the Cantonal Court of Lucerne on May 2, 1957. Subsequently, Kunz did not file an action for the execution of the sales contract before the competent court.
In May 1962, Mrs. von Moos filed an action before the District Court of Zurich against Kunz, seeking to have the sales contract of May 14, 1956 "declared null and therefore to be annulled". She argued that the contract had an unlawful and impossible content, that it did not comply with the prescribed forms, and that it did not correspond to the will of the deceased.
Considerations
The District Court of Zurich dismissed the claim on the grounds that, according to Art. 602 CC, it should have been filed jointly by the plaintiff and her sister as co-heirs. The Cantonal Court of Zurich upheld this judgment, considering that the disputed contract constituted an indivisible unit and that, therefore, a declaratory judgment on its validity or nullity could only be…