Final answer:
Macbeth hesitates to kill Duncan due to the double trust he holds as both his kinsman and subject, as well as his host.
Step-by-step explanation:
The "double trust" that makes Macbeth hesitate to kill Duncan is twofold. First, Macbeth is Duncan's kinsman and subject, which creates a sense of loyalty and duty towards him. Macbeth recognizes that it goes against his role as a loyal subject to kill his own king. Second, Macbeth is Duncan's host, and it is his responsibility to protect Duncan within his own home. Killing him would be a betrayal of the hospitality and trust that Duncan has placed in Macbeth.