>>5222221 (lb)
First, The FBI is a part of the Dept. of Justice. The Attorney General is the Head of the DOJ and is a cabinet member. The FBI is only a Law enforcement agency and are subservient to both the Attorney General and POTUS. The FBI has NO jurisdiction or mandate to use the 25th amendment, Cabinet members - the Vice President and Heads of Dept's, DOJ, State dept, Energy Dept etc are cabinet members. The 25 amendment vests that power to the Cabinet. I hope this helps with your question