"It's alright - this is my first time seeing sibling ribbing in action, so it's very interesting."

All his best friends so far were only children, just like him. He is taking their suspicion in stride - the only way they knew him was one-sided through their brother's admittedly very biased point of view and fawning. It does amuse him that they have such similar habits with the eyebrow and -cchi additions.