It is going to be a very convoluted process so just some general pointers. There are scripts and plugins to merge animations and backgrounds
1. For all processing change the animated gif from Indexed mode to RGB.
2. You will have to work with pairs of images and build up to the final combined 6.
3. Usually images require the same image size (in pixels) and the same number of layers.
4. You can combine the 6 on a transparent background and leave the background image as a final operation.
It might help if you can post one or two of the gif's and some indication of how you intend to place the animations.
1. For all processing change the animated gif from Indexed mode to RGB.
2. You will have to work with pairs of images and build up to the final combined 6.
3. Usually images require the same image size (in pixels) and the same number of layers.
4. You can combine the 6 on a transparent background and leave the background image as a final operation.
It might help if you can post one or two of the gif's and some indication of how you intend to place the animations.