First documented cases of heteropaternal superfecundation in dizygotic twins from the Dominican Republic: A case report

Heteropaternal superfecundation (HSF) is a rare reproductive event where two ova from the same menstrual cycle are fertilized by sperm from different men. This phenomenon challenges conventional assumptions in paternity testing, particularly for dizygotic (DZ) twins. This report describes the first two documented cases of HSF in the Dominican Republic, identified from a review of 61 DZ twin pairs undergoing kinship analysis. Genetic analysis using autosomal (aSTR) and Y-chromosome (Y-STR) markers confirmed that in both cases—one involving opposite-sex twins and the other same-sex male twins—the twins shared a mother but had different biological fathers. These findings underscore the critical importance of testing both DZ twins individually in all paternity disputes to prevent erroneous legal and social outcomes. This report serves as a guide for forensic and medical professionals facing similar complex kinship scenarios.