PROJECT SUMMARY/ABSTRACT Most individuals with disabilities have typically developing brothers and sisters. Over the family lifespan, siblings typically share high levels of involvement in each other’s lives, particularly in childhood and in older age. Increasingly, siblings are being recognized by parents, government, and disability service providers as the next generation of caregivers for people with disabilities. Despite the important and life-long roles siblings play in the lives of their brothers and sisters who have special needs, even the most family- friendly agencies often overlook sibling health and well-being. Research documents health risks to family caretakers of people with special needs, and minority family caretakers are disproportionately likely to suffer these risks. While a small number of effective programs and an emerging body of research informs best practices to address the behavioral health needs of siblings across the lifespan, minority siblings face increased barriers to accessing these programs. For the past 30 years, the Sibling Support Project (SSP) has developed a national and international network that provides innovative workshops for siblings and parents to share their challenges and concerns, and to learn effective social-emotional and behavioral health strategies. Access to these in-person workshops is limited by geographic, socio-economic, cultural, and other factors. Our team of researchers, developers, and SSP consultants propose to build and test assistive mobile app technology for developing knowledge, skills, and routines for attending to siblings’ (ages 3-5) social-emotional health and well-being. Age- and culturally- appropriate multimedia content and interactive behavioral skill-building features will allow families to easily access and engage in the intervention at the time and place that best meets their needs. In Phase 1, we will develop and test one module with a focus on establishing and monitoring family routines that include parent/child connection experiences. Using a pre-post within-subjects study design, we will evaluate the tool’s usability, acceptability, and promise of efficacy among an ethnically diverse group of 50 parent/child dyads in a 4-week pilot test of the app. Measures will include parent self-report of family cohesion, parent-child relationship quality, and parent stress; target child’s social-emotional behavior and well-being, parents’ own self-efficacy for supporting the target child’s social-emotional well-being, and engagement in target activities with the child. We will also collect parents’ reports of program usability, their satisfaction with SIBTime at post-test, recommendations for program improvements, and backend usage data. Advisory Board and recruitment partners will complete a measure of Commercial Feasibility and feedback.