Facts
A. X., born on September 17, 1974, and her brother B. X., born on July 25, 1972, have been living with their uncle and his wife, the spouses Y., in R. since 1977 and 1979 respectively. They are the children of the foreign nationals C. and D. X. residing abroad.
After the spouses Y. had filed petitions for the adoption of the two children, the lower guardianship supervisory authority decided on May 8, 1980 (regarding A. X.) and on March 25, 1981 (regarding B. X.) that the adoption petitions would be granted, that the consent of the biological mother would be waived pursuant to Art. 265c of the Swiss Civil Code (ZGB), and that the adoptions would be pronounced. The biological mother D. X. only learned of these decisions after several years.
Considerations
a) The adoption of a child generally requires the consent of the biological parents (Art. 265a para. 1 ZGB). Pursuant to Art. 265c ZGB, consent may only be waived if a parent is unknown, has been absent with unknown whereabouts for a longer period, or is permanently incapable of judgment (para. 1) or if they have not seriously cared for the child (para. 2). If consent is waived for the latter reason, the decision thereon must be communicated to the affected parent (Art. 265d para. 3 ZGB).
b) The legislative amendment that entered into force on April 1, 1973 introduced a challenge action (Arts. 269, 269a and 269b ZGB). However, the challenge action is also subject to a time limit; it must be filed within six months of discovery of the grounds for challenge and in any case within two years of the adoption (Art. 269b ZGB).
c) Pursuant to Art. 269 para. 1 ZGB, the challenge action is expressly provided for in the case…