Start sharing at dinner time. Stand up and announce: "Look what I can do!"
Wiggle, yank and pull to work one side of your underwear down your leg and over your foot. Encourage your 2 brothers to demonstrate their knowledge of this new skill too! Become amazed as your one little brother does it without even standing up. (It helps that his briefs are about 2 sizes too big.)
Ignore the protests of your parents that this is NOT appropriate dinner behavior. They will surely understand once they see the finished result.
And there it is! Your underwear that was moments before exactly where it should be is now dangling from your hand. Wave it around a bit to get the full effect. Sit back down at the dinner table and flop your underwear next to your dinner plate.
For some reason, your parents are not impressed, although your dad does seem to be trying really hard not to smile.