Although many patients with haemophilia may have exactly the same residual clotting factor level, the clinical disease phenotype may vary greatly. This variation may be related to different genetic mutations responsible for haemophilia, environmental influences and co-inheritance of polymorphisms affecting the coagulation system. The study of siblings with haemophilia offers the opportunity to examine additional factors, other than genetic mutation and environment that may impact on the clinical phenotype of haemophilia. We present the unusual case of haemophilia occurring in fraternal triplets. Each of the triplets had a slightly different pattern of bleeding and response to treatment.