They are probably both at the nestbox, one in, one on or very near. Kinda standard peregrine behaviour - better that both aren't caught in the box by a rival or predator. Besides, other than for nesting, the box is of no interest to them, they probably spend more time on the cross-bar outside or on top than they do inside over the course of the year ... even when its raining or snowing, neither of which seem to bother them overly much.