Yep! Simply have two notifiers (or pairs of notifiers), one for each person, and use Auto Pause schedules for the hours they shouldn't be used — i.e. so one is paused when the other is available, and vice versa. Then assign both to each relevant test.

You can use a similar technique to use different wordings or send different kinds of notifications (e.g. text message during the day, email during the night).