You recognize that your behavior is wrong. You also recognize that your emotional reactions are abnormal. Since you have identified those problem areas and have even drawn conclusions about them, it is important to seek an objective critique. I would suggest seeing a therapist who can validate whether the conclusions you have drawn about your behavior and emotional reactions are accurate. It is important to be correct in your thinking.
As a child and a young adult, you took advantage of family members and said “horrible things just to watch them cry.” Virtually all children have said mean things to family members and learned later to control this hurtful behavior.
You also stated that you mimic an appropriate emotional response when interacting with strangers. You may not authentically feel those emotions but it can be difficult to feel emotionally connected to strangers. Those instances may be indicative of a potential problem but without external validation from a trained mental health professional, it is difficult to know with certainty. A therapist can also examine all aspects of your life including your relationships, whether you have other mental health symptoms, whether you are generally a happy person, and much more. In therapy, it is important to examine all aspects of your life to determine whether the problems you have identified are in fact problems that require treatment.
Just as an individual who experiences an irregular heartbeat (potentially indicative of a heart problem) should be evaluated by a medical professional, you should seek external validation from a mental health professional to determine if you have a psychological problem that requires treatment. It is the next logical step. If your thinking is incorrect, then any conclusions you will draw will also be incorrect. Please take care.