This chapter delineates how entrepreneurial families can build engagement through entrepreneurship by developing or investing in new sustainable ventures. Sustainable ventures strive for the dignity and long-term survival of our planet. They are out most important since human activities affect the life and balance of social-ecological systems on our planet. We thereby propose that engagement is essential for capturing the opportunities for sustainable venturing that emerge in interactions and connections between individuals, family, business and the earth's biosphere. Such engagement facilitates the development of a business purpose that includes and goes beyond financial profits. We connect insights from the family entrepreneurship literature with those from the sustainability literature and suggest three sustainable venturing processes that can help develop engagement with entrepreneurship in the business family. We call these processes igniting family entrepreneurship through sustainability; interplaying between family entrepreneurship and a purpose for sustainability; and interfacing between family entrepreneurship and sustainability. Through these processes, we argue that sustainability provides an opportunity of involving different generations and branches of a family to build commitment around a purpose, and shared values and principles in new sustainable ventures that stretch beyond the traditional financial goals of the business.