I guess I’m still not clear exactly what you are asking. If you want two images to have the same motion meaning that they move in the exact same way you can easily create the desired motion on one object using keyframes. Once happy, simply copy that event, and do a “paste event attributes” to the 2nd image. The movement of the two images will be the same.
However, if you mean you want to join two images together and make them move as one image as if they are just a single image, it might be easier to simply do the combining in an image editor like Photoshop. But again, this may not be what you want.
Perhaps someone familiar with Premier might be able to answer.
wwaag