Since others have talked about grief and handling that I want address how to think about this situation. You frame the problem as, "you have to support three women". This will sound insensitive but that's not my intention. You do not have to support them. Instead I think you want to support them. It's a choice to make to do because there is no external compelling force like the government that's forcing you to it. Instead it's a cultural sense of family obligation that's driving you to do this. So realize first and foremost you have choice in this matter.

As parent it's one of the cruelest things I see in many cultures where parents burden their children in a way they were never burdened by their own parents. You say your dad had a good job but instead of investing in life insurance or the future he invested in iPhone and possibly other useless trinkets instead of a solid investment in the family stability. Now the worst case scenario has happened these failure are now a burden you must bare.

Since it seems you will choose accept this, it's quite likely you'll never have a family of your own. If you don't moderate the expectations of your family they will grind you too dust and happily take anything thing you give. You should have an honest conversation with them about what you're able to do and what you're not able to do and that the lifestyle must be different. Possibly they need to get jobs.

You need to consider long and hard about what you can do and how much of your future you're going to sacrifice for them. It's not wrong of you to consider yourself first. It's never wrong to do that. Because if you can't care for yourself then you can't ever care for anyone else.

I know this is blunt and I've traveled the world enough to know this goes against many cultures, but the time for that cultural mindset is changing. No longer is caring for the parents simply having them in village or in your home and giving them space and food. The modern expenses are much greater and therefore that cultural idea breaks down. Stealing 30 years of your child's adult life is unforgivable, I say that as a parent, especially when that part of your life is time you need to be earning money and establishing your own family.

If you were 50 and had raised your own kids and then taking care of your parents that's different because you've established your lineage.