I don't have siblings so I'm not the best to answer but those actions got me thinking.
Responses to the punches or similar actions:
1. "Even though you're as sensitive as a brick I hope you never get this disease."
2. "I hope you get this disease so then you'll understand."
3. "You know we're family, right? Some get this later in life. Wanna hear the stats on that?"
4. "Wuss? I brought with me 150 sharp needles so sit down for a few minutes (oh, and take off your shirt for a bit) and I'll explain in detail. Hey, where you going? Wuss."
