Is it permissible to participate in a tender for a company I work for, through a company owned by one of my relatives, knowing that I am only aware of the technical matters and the estimated value, and the suppliers' prices are in sealed envelopes?

Since the bidder is not participating in his own name, but through a company belonging to one of his relatives, it is understood that his own company prevents him from participating. If this is the case, then it is not permissible for him for him to participate, whether in his own name or in the name of his relative's company. This is especially true given that he is privy to technical matters and the estimated value of the price, which gives him an advantage over the other participants in the tender.