Trevor spent the first four years of his life living with various family members and in various foster homes. Maggie, his second cousin, adopted Trevor about six months ago. Although she provides him with love, support, and stimulation, Trevor does not seem attached to her. He resists any kind of affection and prefers to be by himself rather than socialize with his new family. According to the DSM-5, Trevor probably has:

reactive attachment disorder

Explanation:

DSM-5 is the Diagnostic and Statistical Manual of Mental Disorders handbook that contains all the information and serves as an authoritative guide to the diagnosis of mental disorders. Using this handbook we can say that Trevor probably has a reactive attachment disorder. This disorder, also known as RAD is a condition in which the individual (usually a child) is unable to establish a healthy attachment with their parent or primary caretaker. Which is the case in this scenario since Trevor is unable to form a connection with Maggie even though she has always taken care of him.