The best result would require creating
custom animations for this.
If the avatars will be fixed in these positions the following may work. Start with existing avatar animations (e.g. one standing, one sitting) and manipulate the avatar skeletons so one is inspecting the other's jaw. There's a demo included in
Teacher in a book that allows you to see the results of applying transformations to individual avatar bones. This will not allow you to create new animations, it will just allow you to put the avatars into specific poses.