Background: Precursors of cardiovascular diseases (CVD) originate in childhood. We investigated relationships of children's CVD risk factors with parent's socio-economic position (SEP) and lifestyle and how CVD risk factors correlate within families. Methods: We studied 602 families with 2141 individuals comprising two full sibs; aged 5–14 years, and their biological parents (Uppsala Family Study). Parental SEP (occupational class and education) and lifestyle habits [smoking, physical activity (PA), alcohol consumption] were taken from questionnaires. Associations with cholesterol, ApoB/ApoA1, leptin, adiponectin, blood pressure, body mass index (BMI) and overweight/obesity (OW/OB) were analysed by linear/logistic regression. Results were adjusted for child's age, gender, pubertal stage and family clustering. Results: We observed no consistent associations between parental SEP and children's CVD risk factors. Parental lifestyle had stronger effects, independent of parental SEP. Children of smoking fathers had higher BMI (4%, 95% CI 1–7%) and leptin levels (27%, 95% CI 1.00–61.60%). Children of mothers reporting vigorous PA had lower BMI, cholesterol and decreased odds for OW/OB with a possible dose effect. Compared with mothers reporting no vigorous activity, mothers with ≤75 min and 76–150 min/week of vigorous activity had 43% (OR 0.57, 95% CI 0.22–0.89) and 72% (OR 0.28, 95% CI 0.14–0.60) lower risk of having an OW/OB child, respectively, after adjustment for confounders. Independent, consistently stronger and significant associations were found between all studied parents’ and children's CVD risk factors. Conclusion: Parental behaviours: smoking, alcohol consumption, low PA are associated with higher levels of CVD risk factors (BMI, OW/OB, cholesterol) in children. Strong correlations in CVD risk factors within families not related to parental SEP/lifestyle suggest a role of genetics in influencing children's CVD risk factors. Public health policies should target families with unhealthy lifestyles.