“Can my parents change their real estate deed to “joint ownership with rights of survivorship” with them, my sister and myself as joint owners even if my parents still have a mortgage on that property? What happens with the mortgage if they pass away together (like an auto crash), can it be “assumed” by my sister and I or will we have to pay off the mortgage in order to keep the property for future generations?”

So you’re hoping that the answer will be that when they die the mortgage company just goes away? Sorry, no. They’re in the business of getting their money repaid, with interest.

Second, even if it doesn’t, you and your sister take the property “subject to” any known liens. So even when your parents are gone, the property still serves as collateral. If you let the loan go into foreclosure, it probably won’t be reflected on your credit, but the bank will still get the land back from you.