In Season 9, Pratt begins an off/on relationship with fellow physician, Dr. Jing-Mei "Deb" Chen. During the series, it was revealed that Pratt had a mentally handicapped adopted brother named Leon living with him, a man who kept Pratt safe and focused on school during his childhood but was left with the reasoning ability of a small child after surviving a gunshot to the head. Due to his handicap, Leon often got into trouble and would disrupt Pratt's professional and personal life, especially when he became involved with a group of thugs who stabbed him in the buttock over a confiscated gun, got him thrown in jail overnight, and then made him join them on a robbery that ended with one of the thugs dead and a cop badly injured (though he recovered thanks to good surgical work by Dr. Elizabeth Corday). To help give Pratt a break, Carter suggested that Leon leave town for a while, leading Pratt to send his brother away to stay with other family members in Baltimore. Leon never returned to the show and was not mentioned again in future seasons. Pratt and medical student Michael Gallant were briefly held for questioning by the Chicago police after a robbery/homicide occurred at a diner across the street; Chen had said that she might have seen a black man fleeing the scene.