regardless what brother has been given notice of, it does not allow for an eviction of the OP for allowing him to visit the premises unless there is something quite specific in the lease prohibiting a tenant from allowing certain people from visiting their abode.
Either there is something missing in what is presented here or LL is stepping way beyond his rights.
but the claim is OP allowed brother to stay at her apartment. Again, unless the lease does not allow any overnight guests, that one is going to be hard for the LL to prove, at least based on what has been presented.

