These are the 2 cases:
1) sponsor mother only. Your income requirement need to include yourself, your immidate family and both of your parents.
Father and mother both need to do Biometric. Both father and mother need to do medical exam and pay for both exams and it will only be valid for 1 year. Need to apply for both police certificates (and pay). Need to wait for background check for both. If everything is good, mother get PR.
In the future, she can sponsor father to become PR but medical, police and background checks will all need to be redone.
2) sponsor both parents. Your income requirement need to include yourself, your immidate family and both of your parents. (same as 1)
All the exams and checks are the same as 1. If everything is good, both parents get PR.