Grouping stacked objects

Grouped objects must be stacked in succession on the same layer of the artwork; therefore, grouping may change the layering of objects and their stacking order on a given layer. (See Stacking objects and About layers.)

Grouped objects are stacked together behind the frontmost object in the group. If you group two objects that are separated by a nongrouped object in the stacking order, the nongrouped object is moved behind the grouped objects.