Samneric are twins who were trapped on the island, just like everyone else that weas stranded on the island. They are twins and are very loyal to the other boys on the island, and act very similar, hence the name "Samneric." Their good former friend Piggy was so nice to them. Roger was so mean to them because they don't approve his ship. Edit
Samneric are caught by Jack's tribe when Piggy Ralph, and them go to Jack's tribe location to retrieve Piggy's stolen specs.