The short answer is yes. Here's the long answer.
Let's say that you already manage your Sprint account through your online profile. Here are the steps for you to add another account so that you can see them both online when you log in.
1. Log into sprint.com and click on the My Preferences tab
2. In the lower section of your screen, click on the "Update or add another account" link
3. This will pop up a screen which shows you the account you already have associated with your online profile. Click the gray "Add another account" button.
4. Enter the account number and PIN and then give your account a nickname for easy identification. Click "Save" then "Manage accounts" and you will see your account added.
5. You can flip between accounts by using the dropdown arrows in the upper right hand corner of the page.