Ralph is clearly not interested in Piggy when they first meet. Ralph is busy trying to work out what has happened and where they are. Even though Piggy knows some of the answers, Ralph is clearly not paying much attention to this fat boy who stumbled out of the woods. Golding writes that Ralph "tried to be offhand and not too obviously uninterested, but the fat boy hurried after him." Piggy is desperate for some companionship and reassurance but Ralph is more concerned with other things.
Piggy asks Ralph his name but Ralph doesn't return the favor. When Piggy has to retreat into the jungle to relieve himself, Ralph doesn't wait around for him. The one time that Ralph demonstrates some interest in Piggy is when Piggy tells him his nickname. This amuses Ralph to no end. His attitude towards Piggy is confirmed again when, even though Piggy begged him not to tell anyone, he immediately tells the other boys that he is called Piggy.
As the chapter goes on, Ralph seems to gain some interest in Piggy since Piggy seems to have a lot of answers about things and about their situation, but he still doesn't have any real affection for him. This comes far later in the book once Ralph and Piggy become more isolated from Jack and the rest of the hunters.
At the beginning Ralph has a mixed and shaky relationship with Piggy. He acts in a condescending way towards Piggy and seems to think of himself as the superior. However, he still allows Piggy to get close to him and become friends because he values Piggy's intelligence. In some sense the reader can visualize how Ralph shares a brother like relationship with Piggy, albeit a little brother. Although he bullies and talks down to Piggy, in the end he still values Piggy and wants to keep him around.