Why is Ralph so concerned about the littluns?

Answer 1

The following conversation takes place between Ralph and Jack, at the meeting in chapter 6: Beast from Air, and explains why Ralph was concerned, I quote...

"Let's be moving," said Jack restlessly, "we're wasting time."
"No we're not. What about the littluns?"
"Sucks to the littluns!"
"Someone's got to look after them."
"Nobody has so far."
"There was no need! Now there is. Piggy'll look after them."

Until this point the boys had no reason to suppose that there was anything more dangerous on the island that pigs. Ralph had therefore felt that the littluns could be largely left to their own devices. With the report from Samneric that they had actually seen, and been chased by, a real beast with claws, teeth and wings, Ralph felt that there was now a genuine reason why the littluns should be 'protected.'

Answer 2

He pretty much treats them like they are his pets. He tries to get them to do things around the island to help out, but they just sit around and play all day.

Answer 3

Ralph does notice that some of the younger buys are frightened. He does not want to leave the little boys alone.