For all the Committee knows, your brother could be a FIFO worker or airline employee who comes and goes and shares your flat when he’s in town. You’ve probably told them differently, but the FIFO scenario is not materially different to your actual situation. You’re entitled to have a tenant and your tenant is entitled to access the facilities. As Jimmy has suggested, formalise the tenancy and then start proceedings towards mediation on the grounds that they are denying access to your legitimate tenant. If you have a SM, you might ask that person to intervene also. If the SM is any good, he or she will know the law around tenancy rights in strata.