Well, I wouldn't say he was "entrusted" with the healing of Justin. I disagree. To give over (something) to another for care, protection, or performance
I firmly believe that Jennifer entrusted Justin to Brian. Justin was 18, but he was not ready to live on his own, nor was he capable of doing so. Her words were take my son...touch him and help him to be touched.
Justin, in many ways entrusted himself into Brian's care. I am not talking child/parent, but definately Brian did watch out for, guide (while Brian was very good at dancing lessons and walking downt he street, he had a very short repetoire when it came to how to deal with pain)and try and help Justin, and in the process learned extensively about himself and gained courage from Justin, but I argue that Justin was entrusted, by his mother, and himself, to Brian.