I think Sam definitely looks up to Callum like a big brother, and Callum clearly has a genuine soft spot for him. It's nice as there are very few friendships this year. Luke A and Adam's developing friendship was one if the mist subtly enjoyable things last year. Not high drama and explosions, but a real mutual friendship developing over the weeks. In the early seasons lots of real friendships developed... but not any more.
What was absolutely disgusting... was Jackie trying to turn Sam against Callum! They were slatng him and Sam quite sweetly spoke up like "...I don't know what's so bad, I like him

" and Jackie basically responded saying that's because he's young and naive, and if he was older and wiser like her he wouldn't like him. Sly! telling a young boy that "if he was more mature and wise" he would ditch a friend.