However, even with TCP, your seating benefits from your status don't apply to the passengers without status on seperate bookings. It only applies to passengers on your booking. For the other booking, flights booked in classes E, N, O or Q are paid seat selection unless at least one of the passengers is Silver or above. If agents have waived this fee in the past then that is not policy but rather an exception (unless the seat selection was free anyway) so you might have to do the trusty HUACA trick until you get an agent who can help.