Relative clauses are types of dependent clauses complete independent sentences - they usually refer to a single word and modify them. Here, in this excerpt, the relative clause would be that we can see in nature. Relative clauses usually begin with pronouns such as who, what, that, etc.
Twins have a strong connection to one another. Golding demonstrates this connection by saying samneric.
"Sam and Eric are 2 young twins that do everything together"<span />