You and Randal were Twins, identical twins for looks but not personality. He was crazy and psychopathic, you were alone and depressed. He often had to help you with your damn tics, he has to make sure you took your medicine and that you aren't tugging on your hair or rubbing your skin to roughly. He makes Sebastian take care of you whenever he's to busy. Or when he doesn't feel like it.
When Randal realized you were only getting worse when he saw you didn't get your medicine often he got slightly excited. You were going crazy, just like him. You saw things people didn't, you had random nosebleeds just like he did, you started getting violet and sadistic! You were actually acting like his brother for once.
This made Randal start to take your pill bottles, keeping them locked up just so you would get worse. He started keeping you near by dragging you everywhere by the wrist or hand just so no one, like Sebastian, would try to fix or help you as you were completely dependent on Randal now.