Independent 80 year old parents built onto my house

Hi Brooke,
Im trying to model out some thoughts and feelings i am having regarding my parents building onto my house and they will live here until they are gone. There are so many things going on in my head that i cant separate them to get clearer models. I feel i need to give you some background information to help me through this. These are all circumstances :
I love my parents
My parents always lived a very high on the hog life style because my dad was able to support that
My parents have emotionally and financially supported my 50 year old sister her whole life including through her marriage, kids, and divorce (huge enabling)
Now my dad is retired from his lucrative accounting practice but still teaches at a university for extra money
Turns out 3 years ago they really did not have enough money to continue their lifestyle and even their current housing situation due to their lifestyle and massive support of younger sister and at times my older sister
I allowed them to build onto my home (2000 sq feet) because it was too expensive for them to live where they were, renting was out of the question for my dad as he was afraid if he died first my mom could not live in a beautiful apartment or smaller condo ( even at this point my dad refused to have my mom live in something not to the standards she was familiar with.
After many thoughts and options I agreed to let them build a beautiful addition onto my home.
They put most all their money into it. (Like their beautiful condo they left but just a lot less money because they built on my land)
I was excited about it then because i felt like i was being the perfect daughter out of the 3 daughters as i have always bern seen)
I knew i would be able to live with them.
I looked forward to it.
Fast forward to present:
Thoughts: how could i have not so blantanly thought about the future?
My parents live here and they have no social life here and quickly will come a time they will not be able to see old friends because they will not be independent due to age.
Me and my husband will be the sole care takers of them if they are to become disabled or when one is left alone disabled.
They have no other life here except us, their grandchikdren, and great grandchildren ( who rightly have their own lives)
This will impact my life in a huge way as i will be the sole care taker and i will loose my life because i cannot have both or one of them isolated at the end of their lives not having contemporaries to be around.
I will loose my independence
My husband and i downsized to this house and its huge! I didnt pkan to move again someday. This mother daughter house will be so hard to sell.
HOW COULD MY PARENTS HAVE BEEN SO SELFISH TO ALLOW ME TO GIVE INTO THIS IDEA OF MOVING IN WITH ME?!!!! They could never allowed themselves to live in a smaller more affordable place because they wouldnt have liked that. I asked them for nothing my whole life like my sisters and now their life choices leading to their life circumstances with lack of money led them to building onto my house! Neither sister will be able to help financially and very little physically due to their location. My life has always been so good and the other shoe will drop for me in my future life. YES, i allowed it and was so dumb not to think about the reality for my future. But….. how could they allow their future needs cloud their daughters future life. I was feeling badly for their situation they created.
I know i let this all happen. How do i deal with this?
Feelings: resentment, taken advantage of, resent sister they enabled, worry and angry at the thought if how she will support herself someday.
Hurt that my parents put their needs before mine because i had the financial stability to allow them to build on and live here.
Basically, i love my parents, i would never want to trade places with my sisters lives, my parents circumstances due to my parents supporting them now has inpacted me and my future. I feel like i have the circumstances of the. Life they led and what their present lives are now here with me.

???? So much

Thank you