I know of a case where the parents were adamantly opposed to the shidduch that their child wanted. The parents tried to persuade the child not to go ahead with the shidduch. When the parents saw that the child was totally committed and would not back down, the father went with the child to Rav Chaim Kanievsky and asked Rav Chaim for his eitzah. Rav Chaim gave his eitzah (to let the child do what he felt was right – even though to the average JOE it would have seemed perfectly reasonable to agree with the parents) and the parents went along with the child’s wish……….
and they happily ever after!