We've all been there. When your hand is two inches too far from the remote. When you really do not feel like doing the dishes. When you can't even think about cleaning your room. One of the advantages of having a sibling, is (besides the companionship, love and everlasting bond between you) is the pure devotion of a younger sibling to an older sibling. With a little help, the older sibling can turn this devotion into adoration, plus a little help.

[edit] Steps

Analyze your sibling. Think. If he/she is older, you might want to say- "you clean the dishes this time, and I'll walk the dog for you." If he/she is younger, you can say, " Please can you help me clean my room? We can do it together. You and me. And afterwards, maybe, we can play Candy land." Another thing that works with little kids, is telling them that it's a "big kid thing." They'll never want it so much ever again.
Be nice. Maybe be a little nicer to the kid, so you can bring it up when you talk to them.
Listen. When at first he/she protests, listen to her/him, but then follow that with your prepared argument.
Never yell. Always smile and talk as if you and they were equals.
Make a deal. When they agree, promise them something - a game, a small treat, etc.
Stay sweet. A spoonful of sugar makes the medicine go down. Turn the task into a game.
Thank your sibling and tell them how grateful you are.