A fraternal twin is either one of a pair of twins who don't look like each other. Although fraternal twins hang out in the womb and are born together, they actually develop from different fertilized eggs and don’t share the exact same genetic material.
When people think of twins, they usually think of identical twins, the ones who develop from the same egg and look exactly alike. But fraternal twins develop from different eggs and don’t look identical, though they might resemble each other, like any siblings. Unlike identical twins, fraternal twins are not necessarily the same gender: even though fraternal also means “brotherly,” fraternal twins are often a boy and a girl.