A strong family social network provides access to support and resources, and is linked to better outcomes for children's health, development and wellbeing. This report describes the process of developing a Children's Headline Indicator designed to measure the quality of families' social interactions. It presents research evidence on the importance of the quality of family social networks for children's outcomes, assesses potential indicators and data sources, and recommends an indicator based on the ability of a family to get help when needed.