If Herbert is snoozing in a favourite spot, Arthur will often jump up and attempt to take the spot over. Herbert will often just move to a new place, or sometimes they will end up sharing.
I have a sense that it is better for me not to interfere, as the cats will work things out. Herbert is no pushover and weighs several pounds more than Arthur.
As well they sometimes seem to become more serious in their play together than I like to see, with definite hissing, and fur flying. Arthur is quicker and more agile, but Herb definitely has an advantage in being able to hold him down if needed.
Once this past month I did intervene and put Arthur in a closed bedroom for a cooling off time, as Herbert seemed tired and harrassed by the fighting.
For the most part the cats are happy together. I often see them grooming one another, and they often will choose to sleep near to one another. I think it must be abit of maturing on the part of Arthur, that causes him to try to best his older friend.