Online fraud substantially harms individuals and seniors are disproportionately targeted. While family is crucial for seniors, little research has empirically examined how they protect seniors against fraud. To address this gap, we employed an inductive thematic analysis of 124 posts and 16,872 comments on RedNote (Xiaohongshu), exploring the family support ecosystem for senior-targeted online fraud in China. We develop a taxonomy of senior-targeted online fraud from a familial perspective, revealing younger members often spot frauds hard for seniors to detect, such as unusual charges. Younger family members fulfill multiple safeguarding roles, including preventative measures, fraud identification, fraud persuasion, loss recovery, and education. They also encounter numerous challenges, such as seniors' refusal of help and considerable mental and financial stress. Drawing on these, we develop a conceptual framework to characterize family support in senior-targeted fraud, and outline implications for researchers and practitioners to consider the broader stakeholder ecosystem and cultural aspects.