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Abstract Purpose: In this research, I report the relationship between S. ovuncatum, S. sinensium, S. japonicum, S. mekongi, and S. malayensis. In addition, I also report the kinship relationship between five Oncomelania species, with Neotricula aperta, Robertsiella spp, and Tricula spp. Furthermore, I describe the formation of the genus Oncomelania from its precursor forms. Principal Results: Results of nucleotide BLAST showed S. ovuncatum shared a 99.69% identity similar to S. sinensium, 98.68% with S. mekongi, 97.98% with S. malayensis, and 97.85% with S. japonicum. The tree-view slanted cladogram showed that S. sinensium is a sister to S. ovuncatum. It split into S. japonicum. Schistosoma japonicum splits into S. mekongi and S. malayensis. Results also showed Oncomelania robertsoni shared an 86.12% identity similar to Neotricula aperta, 85.88% with Robertsiella spp., and then 85.28% with Tricula bollingi. The tree-view slanted cladogram showed that Tricula spp. split into N. aperta and Robertsiella spp. This study suggested that Oncomelania rose from its antecedent forms. Conclusions: Nucleotide BLAST results showed that S. ovuncatum is close to S. sinensium. Schistosoma sinensium split into S. japonicum, S. mekongi, and S. malayensis. Oncomelania robertsoni was close to N. aperta, Robertsiella spp., and then to Tricula spp (Tricula bollingi). Oncomelania species rose from their antecedent forms.