Before the events of Touch, Andre was shot, causing significant brain damage and leaving him brain damaged. Andre and Elliot's father soon abandoned them, and from that point on, Elliot had to provide for the both of them.
Andre is seen in Music of the Spheres. Elliot takes Jake and Martin back to his home in hopes that somehow, they can help his brother regain the ability to communicate. It appears at first that only Jake and Andre are capable of communicating with each other but Andre communicates with Elliot by typing in the word "hungry" (via the app that Martin showed Jake earlier), making his brother happy. At the end of the episode, Andre is seen with Elliot, Felipe, and Yarah getting ready for dinner at the table.
(To be added)