Yes, it is possible for same-sex fraternal twins to look extremely similar. Like any siblings, fraternal twins are the products of two separately fertilized eggs from the same mother and father. They are genetically as similar as other non-twin siblings. By chance, they could look very similar, or very different, just as non-twin siblings can look very similar or very different. Fraternal twins may look more similar than non-twin siblings because they are the same age, and because they share the same environment (such as prenatal and postnatal nutrition).