Frankie is a laid back tom cat - into everything and friendly and chatty.
http://i151.photobucket.com/albums/s136/wolf63 /kingofthecastlesmall.jpg
Merlin is a long haired cat who likes to sleep and eat and do nothing else.
http://i151.photobucket.com/albums/s136/wolf63 /Merlinonprintersmall.jpg
They were feral kittens, rescued by the Cats Protection when they were very young. They are full brother and sister but neither look alike or are at all alike in character.
Frankie wants to play and teases Merlin - who just tells him to go away. Eventually the claws come out and Frankie runs off to lick his wounds.
I used to thing that when they were running around they were playing and enjoying themselves. I think that Frankie is playing and Merlin is just trying to get away from him.
Luckily I live in a large flat which is over two floors. They can avoid each other when they want. Other times they are so friendly. They are typical siblings.