At-home DNA testing remains popular amongst individuals today. These direct-toconsumer services come with several privacy risks, that can extend far beyond the individuals taking the test. How do participants attribute risk to biological family members? How do users and non-users differ in comfort with their data being shared, and their understanding of privacy risks? How do privacy perceptions differ for ancestry and health data? To investigate these questions, we conducted a 2 × 2 survey, and discovered non-users were significantly more privacy conscious, and that health data was considered more beneficial overall. We then interviewed 10 biological family members of users who had not taken a test themselves; though many were unconcerned or indifferent towards privacy, privacy-conscious participants were frustrated by, and resigned to, the loss of control over their data. We discuss our findings, the implications of our research, offer recommendations to improve privacy, and identify areas for future research.This thesis is the result of support and guidance from many over the years. To my supervisor, Sonia Chiasson: I would never have found my love for research and HCI had I not stumbled across CHORUS as an undergraduate in 2015. You have my deepest gratitude, for the infinite patience, feedback, and guidance. You are a stellar mentor, and have always been there for your students (rain or shine). I feel privileged to have been mentored by you, and am looking forward to all the future research yet to come! (Also, have this:).To my committee members, Elizabeth Stobert and Hussein Al Osman: thank you for your insights and feedback which helped improve this thesis. I would also like to thank Alan Tsang for chairing the defence, and my participants for their time.To everyone at CHORUS: thank you for your feedback at practice sessions, listening to me talk about my thesis at every lab meeting, and for all the laughs.To my friends: FW, DN; the many work sessions (and non-work chats!) we did helped produce this thesis. Reham; I could not have done this without your emotional support. Thank you for all the hours where we sat together, had some chai (taye), and discussed various aspects of this research (and life). JS, HL, and all my friends; thank you for the many conversations and jokes that kept me smiling.To the Baig/Bru families here: thank you making sure I was fed, for the sweets, games, and visits. To my family back home; as I stressed about deadlines, you all stressed with me :). Nano; your songs gave my heart "thandak". Thank you all for the unwavering support, even as I was unavailable to meet or answer phone calls.James: thank you for your incredible patience, for staying up late with me, and giving me stellar graphic design advice. Knowing that I could turn to you for rubberducking and/or assistance, or a laugh and hug, made everything much easier.Baba: around ten years ago, you and mama made a difficult choice, and provided your children with an opportunity many don't have. Without you I would not be here, ...