This research relies on a theoretical approach that combines socio-emotional wealth and social contagion theories, suggesting that family dynamics and the diffusion of values may explain why some firms engage in accounting for and reporting on the UN Sustainable Development Goals (SDGs). In particular, this chapter explores why two small UK-based family businesses chose to report on the SDGs, with a focus on the transmission of sustainable values and culture. This research adopts an interpretive case study approach, using interviews, documents, and online sources. Our results show that the UK-based family businesses under investigation implement a proactive sustainable philosophy, by actively reporting on SDGs, emphasizing transparency, and employing a bottom-up reporting approach. Motivations include family-driven passion and a desire “to inspire others”. Challenges consist of the presence of diverse reporting frameworks and barriers for small businesses. This research progresses and nurtures the academic debate on: (1) the drivers for the implementation of SDGs from small family businesses; (2) transmission of sustainable values via the “social contagion” process within small family businesses; (3) the relevance of accounting and “Accounting for Sustainable Development” practices and reporting within family firms.