Animation of several objects depend on main object I would like to animate a clothed human model. The human geometry is rigged, but I dont know how to add additional objects to the human rig.

I want the t-shirts and pants movement to follow the human's poses.
It is possible to parent multiple objects to the same armature. Simply repeat whichever method you used to parent the human to the rig on the clothing. 

For example: Select the clothing and then shift select the rig and press "Ctrl + P" and then select "Armature Deform with Automatic Weights".