Brainy had a hard time voicing his feelings sometimes, but after centuries, Clumsy could understand him. "I was just about to say that," meant, "That's a good idea, Clumsy."
"Get away from me," or any other hurled insult never meant a final goodbye, Brainy wouldn't be upset forever. What it meant was just that Brainy needed a break, to be alone for a bit. He'd always come back, though.
Which led to another point- "I'm glad you're here, Clumsy," after an argument, meant "I'm sorry." Brainy was too proud to apologize or admit he was wrong, but Clumsy could tell when he wanted to.
When Brainy repeated Clumsy's name three times- "Clumsy, Clumsy, Clumsy," sometimes that meant "I can't stay mad at you."
And the brush of fingers against Clumsy's wrist or the small of his back, a hand resting on Clumsy's shoulder, gifts of the first-edition of one of Brainy's new books, and Brainy picking Clumsy to join him in a task despite Clumsy's inclination towards failure- all of that meant "I love you, Clumsy." It meant "I love you, I always have, and I always will."
And Clumsy loved him back. It was hard, sometimes, but worth it.