Linking two armatures into 1 2 models having their own armature,i wish to link both armatures into one ,creating a bone linking both Root bones,making it one armature.

I tried few things,it's ends up messing the mesh.

PS: No constraint.
Select bones of first armature then hold shift and select bones of the second armature and at the end then press ctrl + j. This must be done in object mode. I think this will join two armatures into one.