Dude, it's totally normal to date younger chicks. I know a lot of "older" couples that met when one was in college, the other in high school. I think generally speaking, the ladies like a guy to be a little older than them anyways.
You could use your sister to your advantage and date some of her friends.
"Ignore the ramblings of the ignorant, and step on or over their crumpled bodies as you make your way to the top of the mountain. Eat upon their flesh for fuel, and, through your determination and will, banish them to obscurity and a life of complacency and self righteousness that is the hell in which they live"
-Richard Safreed
"Civilize the mind, but make savage the body."