Final answer:
You cannot turn off parental controls on your sister's Xfinity account simply by creating your own account. The primary account holder, likely your sister, controls these settings and you would need her permission to make changes. Communicate with her directly to discuss adjusting the parental controls.
Step-by-step explanation:
If you create your own Xfinity account, you still may not have the ability to turn off parental controls if your sister has set them up with her account. Parental controls are typically managed by the primary account holder, who has the authority to set and change these restrictions. If you are not the primary account holder, and your sister's account has that status, you'll likely need her permission or assistance to adjust the parental controls settings.
To change parental controls, you would usually need to access the settings through the main account. Every service has its own rules and setups, so the exact steps can vary. In most cases, providers require the person with administrative privileges - often the account creator or the person who pays for the service - to manage such settings to ensure that controls intended for the safety of minors are not bypassed without consent.
If you are looking to adjust these settings for legitimate reasons, such as being of age to not require parental controls or having an agreement with your sister, your best course of action would be to communicate with her directly about changing the controls.