Most chronic care happens at home within families, yet health technologies remain individually focused despite research showing family involvement significantly improves outcomes. In Thai culture, intergenerational caregiving is deeply embedded in family practices, creating a gap between collective care values and individual-centered health tools.

Research Question: How might we design for relational use in health data sharing between Thai adult children and their parents managing chronic conditions?

Grounded in data humanism philosophy that values human stories and lived experiences behind numbers, the study explored data intimacy—the closeness that develops when people share personal data with trust and intention so that loved ones can understand and care for each other. Using participatory design and contextmapping methods, four Thai parent-child pairs (n=8) engaged across two research cycles. Families tracked personal health data, participated in paired co-creation sessions, and designed adaptive sharing approaches for different health situations.

Key Findings: Three interconnected perspectives challenge individual-focused health informatics: First, families exhibit four distinct sharing patterns that adapt over time rather than remaining fixed. Second, health data sharing needs shift across four non-linear phases from stable periods to health crises. Third, families use data as collaborative memory-making tools, combining medical numbers with personal stories.

Contributions: These insights reveal how families naturally practice collaborative sensemaking around health data. The research develops eleven design principles organized around three pillars—designing with relationships, adapting to changing health situations, and honoring lived experiences behind data—with potential for translation into practical tools for health technology design and family conversation facilitation across cultural contexts.

While grounded in Thai parent-child dynamics, validation with design students with diverse backgrounds (n=5) suggests these insights could extend to other close relationships managing health prevention or chronic illness across cultural contexts. The Wave of Care (https://wave-of-care.webflow.io/) website communicates findings through storytelling for design practitioners. Future applications may include family conversation facilitation tools, emotionally safer health sharing approaches, and prevention-focused design that supports gradual health communication and connection before crisis points force difficult conversations.