
Generally, people look, act, sound and move like one another, they tend to notice the similarity at the unconscious level and therefore get along with each other. It is a natural process to help things come in a state of harmony.
If you mirror or match ones voice and posture, blinking and facial expression, words and gesturing, physiology and position you become connected to that person.
Do not worry too much about the other noticing the mirroring, they almost never do if it is done naturally and without too much thought.