Show them that you can handle responsibility. Doing household chores that are assigned to you - if none are assigned, jump in and lend a hand. Sit down and talk to them. Take a mature approach and say "I really want a kitten and I'm ready to prove to you I can handle the responsibility. If you are old enough to work or do odd jobs, offer to pay for the litter pan, litter and food. Just remember, you have to practice what you preach and any pet can be a big responsibility, even for adults. Hope this helps. Good luck.