Is the husband sinful for not informing his wife that her parents, with whom she grew up, are not her biological parents, given that he knows this and is certain that informing her will psychologically harm her?

Adoption is invalid, and the rulings of true filiation, such as inheritance and the prohibition of marriage due to affinity, do not apply to it. The adopted daughter must be informed of the truth of the matter to avoid legal violations, taking into consideration the appropriate method and time so as not to hurt her feelings. And the husband should be a support for his wife in accepting this truth.