I just passed my Canadian citizenship and now I will sponsor my father to be a Canadian Citizen also, however, my dad is still financially supporting my two older brothers who is more than 30 years old and my dad wish to sponsor them to come to Canada after he pass his citizenship. My older brothers is mentally and physically okay, it's just that whatever they make for a living in Philippines is not enough since both of them also have a family to fed and my dad still support them financially, Can my dad possibly petition them afterwards?
Did you even apply for the interest to sponsor back in 2020? (to qualify, you needed to have 3 years of income that's above the LICO for your family size including the PA to be sponsored)
If not, there is no chance that you were selected in the lottery for PGP sponsorship this year (which already happened) and no one knows when PGP will open up again.
So first issue with your post is: being a citizen doesn't allow you to sponsor your father to be a PR. (anyone needs to be PR and live enough time to meet the requirement to apply for citizenship. I though you just went through the process?)
And second, even if your father becomes a PR, he cannot sponsor adult children. There is no way around that. Unless... he some how became a PR,
you died, his parents all passed away, he has no spouse/common law partner and there is no living relative. Then he may be able to sponsor ONE of his adult child.
BUT unless issue one is solved, there is no worry about the second part of the problem.