If your family members have not been on a dependent Visa (F-2, J-2, M-2 or Q-3) in the US during the tax year and have spent the entire year outside the US, you do not need to fill out their information in Sprintax and you will not need to prepare Form 8843 for them.
Info: To remove a dependent on Step 5 About your college, you have to slide the scroll bar all the way to the right side of the table and click on the 'X' option. That will remove the previously added row and you will be able to continue with your application.