This sounds like creating a sub-group and adding multiple instances of it could be of help. Can you tell us - does this group have any rotations configured or is it always the same people in the same order? Knowing this, you can decide if adding people more than once in the shift makes sense or if you just have to notify the primary person in the rotation more than once. At this time we don't have a feature to notify the person x times during an event, but one can lean on device escalations per user in this kind of situation more so than person escalations. Remember, every time we notify a user we abide by that person's device escalations as well. So if we have a primary phone being called first, we can add a secondary phone after 5 minutes so they at least get tried twice. Then we can rely on e-mail, SMS or mobile app depending on what that user has. At the same time you can add a 10 minute delay between primary and secondary users that way we try the primary once, again after 5 minutes then at the 10 minute mark the secondary will get their first notification.
Let us know if that sounds like a direction you can use.