Combining two rigs but keep control over separated objects

So in the end this is going to be used for a game (unity engine). and because of that there must be only one rig, so my question is how do you combine rigs but keep the bones control over there separated


see when i combine the rigs (select bow rig then arm rig ctrl j) i have control of the arm rig and it has its weights but i only have control of the bones of the bow.

there are two bow rigs (for weapon switching)

If you have two bow armatures, and the bones have the same names, this may be causing name conflict.
If you want to keep the bones for each bow, you may have to name the bones differently.