Is a claim by the heirs of the second wife, asserting their right to inheritance after the presentation of a waiver document bearing the wife's fingerprint and written five years before the husband's death, acceptable, especially considering that inheritance only takes place after the death of the deceased?

The wife's heirs are entitled to her share in her husband's inheritance, because waiving the inheritance before the husband's death does not nullify the wife's right to it. This is because inheritance is established after the husband's death, not before it, and according to the most authoritative opinion among scholars, relinquishing a right before it becomes due is not binding.