Foster seems worried about Dalton after he appears in a coma, and strangely says that he doesn't like it when Dalton "walks around" at night.
Insidious: Chapter 2
Foster appears in Insidious' sequel, Insidious Chapter 2. When Josh is possessed and attempts to kill Renai but is hit in the head by a baseball bat by Dalton, who had came back home with Foster. Foster hides in the basement with his brother. Dalton uses his tin-can-phone when he travels to the Further to find his father.