I own two puppies one a 5month old named Rocky and the other a 7 week old named Sense. Rocky puts his head on Sense's body as if Rocky is using him as a pillow. What does this behavior mean?
Rocky is probably doing this as a form of protection or comfort towards Sense. This is nothing to be concerned about! It's most likely a behavior showing companionship and care towards the younger one. Since he's older, he may feel obligated to protect the younger pup. It shouldn't be an issue unless Sense starts to become frustrated or annoyed with Rocky, but he most likely doesn't mind it! I've seen a lot of dog siblings do this with one another.
It means your Rocky is feeling safe by sleeping like this. Many dogs do this. You don't have to worry unless he hurts your other puppy.