A good example is when a husband and wife want to leave everything to the other spouse, they usually make Mirror Wills.
Mirror Wills relates to when both parties have the same Will but in reverse, for example, they leave everything to the other partner and thereafter to the children.
It is not possible to have a joint Will for a couple. Each individual must have their own Will, although the cost of making mirror Wills is usually less than the cost of making two Wills independently.