Marge Mech/Armatures into a single animation

I have 2 different objects with 2 different armatures, and i want to join those 2 armatures together into 1 armature (In the same scene)
and i would also like to know how to add 2 different actions together.

Description:
I have a hard time to get unity to read my animation, it seperates them into serveral single animations.
When this problem accured a few days ago i thought it would be just a single botton or somthing but the problem semse to be a lot more complicated on that unless its just me.
Some people says its the NLA editor in blender and fuse them together.
Other say its the Bones that need to be connected together in somekind of menu.