in the july 22, 2008 episode "," it is revealed that new hospital intern dr. kyle julian is leo's younger brother, and that the two do not get along. the july 29, 2008 episode "" establishes that leo had been adopted around the age of 4 or 5. in "" (9/23/08), their mother patricia notes that though she had been unable to have children and so she and her husband had adopted leo, she had subsequently become pregnant with kyle.