My daughter was married a few months and then divorced. It’s many years later and she has trouble getting dates as we won’t say why. Part of why is public knowledge-his sister publicized multiple incest events. Are we allowed to answer or must we still keep silent?
If your assessment is indeed correct, and the reason that your daughter is not getting suggestions is because you are not willing to explain why she got divorced, then you are allowed to answer.
However the Chafetz Chaim stresses that you have to say it as it is without exaggerating. Also, your intention should not be to degrade him rather to benefit your daughter.
May you have much hatzlacha, and may your daughter stand under the chuppa soon and build a beautiful home filled with much joy and happiness!
Chafetz Chaim: Clal 10 Be’er Mayim Chaim 31 (regarding Gemara Berachos 5b), and Clal 19 Be’er Mayim Chaim 43.
The source for not exaggerating, and for intending only for the benefit and not to degrade, is found in Chafetz Chaim 10:2