Add 2D sprite to an existing animation?

Hi everyone, I'm new to Unity. I've created a 2D animation using sprites (each sprite is manipulated within the animation window to move, rotate, go transparent, etc, I'm NOT using a sprite sheet). I knew I wanted 5 sprites to work together in an animation so I made them children of an empty game object and made sure that they were all highlighted before selecting 'new animation clip' so that I could manipulate all 5 at different points in the animation without the record function stopping (they all show up on the left hand side of the animation window).

A few days later I realized I needed a 6th sprite added to that group animation that moves/responds to the way the other sprites are moving. It would be too difficult to make a completely new animation for that 6th sprite and try to time it precisely with the other animation.

Is there a way to add a new sprite into an existing animation? I don't want to alter the original animation, just add to it.

Thanks!