Is it permissible for the uncles to perform Hajj while being aware of the details of their grandfather's damaged merchandise, which was entrusted to him, and which neither the merchant nor their grandfather disposed of until it spoiled, given that they remain united in the business founded by the grandfather?

The grandfather's possession of the goods is a trust (amanah), and he is only liable for damage if he commits an act of transgression or negligence. If the goods perish after he informs their owner to collect them, he is not liable. The remaining part must be returned to its owner. The uncles' Hajj is valid, though sinful if performed with unlawfully acquired money; otherwise, there is no issue. If the source of the grandfather's money is unknown, it is lawful for the heirs. If it is mixed with unlawful money, the unlawful portion must be disposed of, and the remainder distributed. If all of it is unlawful, it must all be disposed of, for unlawfully acquired wealth does not become pure through inheritance.