Boxwoods and azaleas have some similarity in their requirements but, of interest to you, is that the two shrubs have shallow roots. You can probably grow them together but try not to plant them too close or else their roots will get entangled and begin to compete for resources (food and water).

You do not mention anything about sunlight. I assume that the azaleas will receive morning sun and afternoon shade; the boxwoods can handle full sun but probably do better with a little shade.

Be aware that azaleas also require well draining, moist, acidic soils. Boxwoods require slightly acidic conditions like pH ranges between 6 to 7 and will tolerate other types of pH ranges. Azaleas will be more picky about this so, if your soil is not acidic, consider planting in raised beds instead. See the post script note at the bottom.

As for the space and the question whether it will be enough, well, it will be enough if both types of shrubs are selected based on similar height at maturity. Since you already have boxwoods, choose azaleas that will grow about as tall as the boxwoods. Maybe shoot for 1-3' high Kurume Azaleas?

Just remember that all this depends on meeting the sunlight requirements (morning sun and afternoon shade; dappled sun works well too) and soil requirements (well draining, moist, acidic soils; or use raised beds).

Luis

PS - Concrete from the house and the walkway releases lime as time goes on. Lime helps make soils less acidic so be aware too that you may need to amend the soil there once a year or so in order to prevent the pH from becoming too alkaline (the opposite of acidic). You can get around this problem with raised beds too.