This is a really sweet picture, in terms of the emotional impact it imparts: the punk kid feels lonely, outside of his comfort zone. His clearly innocent younger sister sees past his purple hair and punk rock attitude for who he really is, the cool older brother that makes her laugh.
I could be totally off-base on guessing the story behind this, but that's how I'm interpreting it. I look at this and think "wow, I only wish I could have been so lucky at that age, to have someone who 'gets it.'"
Very nicely drawn, and I love how the parents are utterly oblivious to this random act of sweetness.