I'd stop asking everyday. I did that for years and never got my dog.. then I stopped and my mom started showing interest in a dog slowly. After we got our first dog, I really wanted a second dog. I knew she'd say no so I started taking care of Kai (doing all the feeding, walking, training, etc). Shortly after, we got our second dog. I just recently started taking full responsibility for both dogs (all vet bills, paying for food, walks, training, everything).. which made it much easier for me when we talked about getting a third (we didn't end up adopting him cause my boys didn't get along with him).

So my advice is to stop asking everyday.. and just show them you're ready by devoting more time to your current dog.