Mmmm...so their own funds and cash. Is this all their savings? Do you they have pension/investments/FD to show to counter that not spending all their money to come to Canada.
So that is all their funds? Given two rejections, there is no point in reapplying until they can show more funds in personal accounts. They want to show that they are not spending their savings to come to Canada. So if they have retirement funds, investments etc. then that would be funds to show that they are not depleting their savings.
Are you sponsoring their tickets? If you father is working attach a employer letter. Attach property papers. Explain why he needs to canada by a certain date.
Then it doesn’t make sense that they’ll visit you and use up their entire savings they have just to visit you for 2-3 weeks.
They need to show that their visit won’t materially affect their financial position once they return . Aka , leave them broke.
Even if you become a PR they, the visitors must show financial backing unless you go the SuperVisa route