Objectives: This study aimed to assess suicidal ideation based on gender, age, marital status and heritability coefficient estimate in a sample of 11 to 35 years-old monozygotic and dizygot twins. Method: One hundred and sixteen twins (MZ=66, DZ=50 age, 11-35) were invited to complete the Suicide Ideation Scale (SIS) in the anniversary of Laleh and Ladan. Results: Analysis of variance showed that gender, age and marital status together accounted for 80% of the total variation of suicidal ideation in twins. There were significantly higher rates of suicidal ideation between women, adolescents, and singles in comparison with men, young people, and married people, respectively. The heritability coefficient in adolescent and young twins was 0.49. Conclusion: The findings suggest that women, adolescents and single people, respectively, compared to men, young people and married people are at higher risk of suicidal ideation. Regarding heritability of suicidal ideation, supervising of significant others to people with suicide ideation must be considered in mental health policy making in the field of primary and secondary prevention.