Families of Youth with Developmental Disabilities: a Theory-Based Intervention

Inclusion Criteria: * Participants in all conditions will include mothers, fathers, TD siblings between 11 and 17 years old, and individuals with IDD of any age. * Participants must be able to understand and respond to survey questions in English * Parents must be cohabitating, with both participating children living in their home. * Individual with IDD falls into one or more of the following categories: 1) meets criteria for an intellectual disability, which would mean a measured IQ of 70-75 or lower and a measured Adaptive Functioning score of 70-75 or lower, 2) meets criteria for an Autism Spectrum Disorder based on an evaluation using the ADOS-2, SCQ, and expert clinical judgment based on DSM-5 ASD criteria, or 3) has a medically verified genetic condition (e.g., Down syndrome, Fragile X syndrome, Williams syndrome, Angelman syndrome, others) that is generally considered to be a developmental disability, and shows cognitive or adaptive functioning deficits (70-75 or below) although not necessarily deficits in both categories as would be needed for an Intellectual Disability diagnosis. Exclusion Criteria: * Siblings identified as typically developing will be excluded 1) with a score of 10 or higher on the SCQ-L, if a subsequent ADOS suggests that they have an ASD diagnosis, or 2) with a WASI-II score of 75 or lower.