How do you convince your parents to have another baby?

From my experience I have been begging my mom to have a 4th sibling and she said she doesnt know yet if she would like one but this is how it worked

1. next time you are out shopping show her all of the baby clothes and how cute they are

2. explaing to your parents why you want one

3. do chores be a good-girl

4. point out people with there own babies next time you are out.