Family members will automatically not be scheduled for different shifts on the same weekend. If they are being scheduled for different times on the same weekend, first make sure that the family groupings are set up correct by looking at them closely in the Families pane. Then, choose "Scheduler Settings..." from the Schedule menu of any open schedule window and then make sure the "Don't schedule family members for different shifts on the same weekend" option is turned on. The next time you run a schedule a couple should never be split up for two different shifts on the same weekend.