If your wiggle effect is applied to the position of the first object, then anything parented to it (ie. the child of the first object) should inherit the wiggle. Is the wiggle applied to an effect within the first object? To get the second object to inherit an effect, you’d have to apply the same effect to the second layer and use some expressions to link the parameters.
You could also use an expression to link the position of the second object to the first one; just option-click (or alt-click on a PC) the keyframe stopwatch next to ‘position’ on the second object, then using the curly pickwhip, select the position of the first object. The child object’s position should then say something like:
thisComp.layer(“parent object”).transform.position
If you want to add an offset, you could do something like this (in the second/child object’s position):
x = thisComp.layer(“parent object”).transform.position[0];
y = thisComp.layer(“parent object”).transform.position[1];
[x, y+50]
This will place the child object at the same x position as the parent, but 50 pixels below it (the “y+50”).
Hope that helps.
– Paul