Siblings play an integral role in shaping each other's psychosocial development. Sibling relationships marked by positive, prosocial interactions provide an ideal platform for individuals to acquire essential life skills that will benefit them throughout life. On the other hand, early sibling relationships marked by elevated levels of hostility and conflict can have serious long-term, negative consequences. Of all the factors that influence the sibling relationship, few are as important as parents. Currently, there are no parenting programs that have been co-constructed with parents in the community to help them with improving their children's sibling relationships.This dissertation seeks to make an important contribution to literature by taking on the challenge of developing and evaluating a parenting program for improving sibling relationships.The feature of this body of work is the evaluation of a version of the Triple P-Positive Parenting Program, tailored to the issue of sibling relationships. However, the goal of this dissertation extends beyond an evaluation of program efficacy. This dissertation also examines the process of innovation and engagement throughout the research process. The thesis seeks to demonstrate that innovation and engagement in evidence-based parenting research enhance the capacity to design interventions that fit with community needs and increase the impact of research.Chapter One provides a general introduction to the current body of work. The chapter makes the case for why sibling relationships are worth studying, why parenting programs are a useful tool to improve sibling relationships, and why engaging parents throughout the research process is important. The chapter also articulates an innovation engagement framework that describes the mechanisms associated with linking ideas to impact. Chapter Two provides a model of consumerengaged program development. Using sibling conflict as a case study, the model articulates how evidence-based parenting interventions can be developed in consultation with different members of the community, resulting in benefits to children, families, and the community.Chapter Three presents the outcome data from a national survey of parents on the topic of sibling relationships. The survey bridged an important gap in the literature by incorporating the parent voice as an initial step in designing an intervention for improving sibling relationships. A total of 409 Australian parents completed an online survey relating to their views on sibling behaviours and what, if any, help they desire in dealing with the issue. Parents predominantly required help with conflictual behaviours and attributed the causes of sibling conflict to their child's internal traits, but expressed strong desire for assistance with managing behavioural and verbal problems and reported high levels of acceptability for positive, rather than punitive, parenting strategies. Parents showed a clear preference for parenting interventions delivered in brief, easy to access formats.iii ...