Parenting in animation

If you parent both objects to a null to animate them together then you can animate them individually and together as nuch as you'd like.

Maybe don't parent to one of the objects that is already animated.

Instead, create a new Null Object layer and use that as the parent for all the layers that need to move together. 

You can even use multi–level parenting to link multiple nulls together so that you can stagger your animation.                                                                                       

If you dont understand expressions and how to set up a slider control it would be good to learn 

With the little info you have supplied I would say the simplest solution is to precomp the animated layers and then change the values of the precomp

Mo

Either split the layers or apply an expression driven by a weighting slider to link the animation properties using a linear() function or similar. Certainly some more specific info like a screenshot might help us to tel lyou waht would be best...

Mylenium