>We are really careful to distribute hugs, walks, food and attention evenly
Although that's the natural human instinct, conventional wisdom says that's not the way to go with dogs. Dogs prefer a secure ranking order than equality, so to show your older boy that he hasn't been usurped he should be the one you speak to first, gets his dinner first etc. The time difference need only be a second or two, not minutes, but dogs seem to be much happier that way.
Both dogs sound lovely, and your older boy, though still very much a puppy himself, enjoys having a companion to romp with. :-)