The purpose of this study was to assess the possible effect of recalled traumatic experiences, perceived parental rearing styles, and family parameters on the occurrence of borderline personality disorder (BPD) versus other personality disorders (other-PDs). A total of 88 adult outpatients with personality disorders completed the Traumatic Antecedents Questionnaire and the Egna Minnen av Barndoms Uppfostran, which measures perceptions regarding parental rearing. Results indicated that incidence of traumatic childhood experiences was higher among those in the BPD group compared to those in the other-PD group. Firstborns were less likely to carry a diagnosis of BPD over other-PDs. Also, significantly more BPD compared to other-PD patients reported being the father's favorite child over siblings. Results suggest that traumatic experiences, birth order, and family interactions in the presence of siblings seem to differentially affect the formation of borderline diagnosis compared to other-PDs. Limitations and clinical implications of the study are discussed in detail.