Suicide risk behavior is a significant contributor to the mortality and morbidity of schizophrenia. We previously reported affected sibship status in a Xhosa schizophrenia or schizoaffective disorder sample to be protective in nature; given the counterintuitive nature of this finding, we expanded the sample size to seek further clarification. Subjects were assessed with the Diagnostic Interview for Genetic Studies and then stratified into two groups: with (n = 137) or without (n = 837) a previous suicide attempt. The presence of lifetime bizarre behavior (OR 1.5; 95%CI 1.12–1.87) or cannabis use or abuse (OR 1.2; 95%CI 10.01–1.47) was a significant predictor of suicide attempts, while a higher global alogia score (OR 0.84; 95%CI 0.74–0.96) was a protective factor. Our data seem to support that in this population, encouraging family members to report bizarre behavior and implementing dual diagnosis interventions for cannabis use or abuse could be an appropriate starting point toward developing a targeted suicide prevention program for further research.