Iberia guarantees that for bookings that include children between the ages of 2 and 12 at least one of the companions will automatically be allocated to the same row of seats as the child, or an adjacent row. This also applies to the companion of a passenger with reduced mobility, provided that this person is identified as such when the booking is made.
If you select seats with a surcharge, you do so voluntarily and the additional cost will be non-refundable.