If parents are divorced, then you can sponsor them (and their new family) individually.https://www.canadavisa.com/canada-immigration-discussion-board/threads/sponsor-my-father-or-my-mother.177171/
You can read this thread. Looks like no one is really sure. Also it seems some think you need to meet income requirements for BOTH father and mother ie 2 persons plus yourself and family even if you are only going to sponsor One of them.
To sponsor any of them, you need to meet income requirement for your family + the applicant's family. (i.e. 1 + mother only) for the previous 3 years.
Then to sponsor the other parent, you need to meet income requirement for your family + parent under your sponsorship/undertaking + parent on new application plus any of his/her current spouse and dependents for the previous 3 years. ( 1+1 (mother) + 1 (father) + any of other dependents or spouse of father)
If OP only meet income for 2 in 2016, 2017, 2018 then OP needs to wait till income increase to meet for at least 3 2019, 2020, 2021 and apply in 2022. (if PGP still exist then)