Hiring the brother - if he will be paid with plan assets - is the poster boy for a self-dealing PT under 406(b)(1). See the following example from the DOL regulations.
Example 6. F, a fiduciary of plan P with discretionary authority respecting the management of P, retains S, the son of F, to provide for a fee various kinds of administrative services necessary for the operation of the plan. F has engaged in an act described in section 406(b)(1) of the Act because S is a person in whom F has an interest which may affect the exercise of F's best judgment as a fiduciary. Such act is not exempt under section 408(b)(2) of the Act irrespective of whether the provision of the services by S is exempt.