You may be looking for an expression that maintains the spatial relationship of the two layers. If so, you need an expression like this for the child’s position:
p = thisComp.layer(“parent”).position;
deltaAtZero = p.valueAtTime(0) – position.valueAtTime(0);
p – deltaAtZero
Where “parent” is the name of your parent layer. Now you can move the parent layer and the child will follow, but you can independently rotate or scale the parent.
Dan