My twin brother refused to help with Mom's elderly care costs. Do I have any rights to force him to pay half the costs?

My Mom moved in with me and my husband when my only child was six months old. The doctor said since she had so much going wrong, she would need to have constant care. (Mom suffered from transient eschemic attacks (mini strokes), congestive heart failure, kidney and bladder disease, osteoarthritis, osteoporosis, diverticulosis, pancreatitis and then the hospital dropped her and broke her hip forcing her to walk the rest of her life on a walker) I had been trying to get Mom to move in for several years before this because her health was deteriorating, but Mom was a very independent lady and wanted to do for herself as long as she could. I checked on her twice a day for the ten years before she moved in with me to be sure she was taking her medicine properly and to take her to the grocery store, etc. She also always went on vacations with me and my husband because I was afraid to leave her alone. It was actually easier for me once she moved in. However, she did need care around the clock and I had to quit my job to care for her and my newborn son. I asked my brother to help financially which he screamed at me he didn't have the money (his job paid $22+/hour) so that wasn't true. He was divorced (again) and has three children now 19, 27 and 39 so he was always paying out child support but he never saw his children after he divorced their mothers. I helped raise all three of his children, including having these kids live with me at various times. The 19 year old is still living with me so he can go to college on a grant because his father disinherited him. Now, out of the blue, my brother calls to inform us that he has two - three months to live (terminal throat and liver cancer from smoking and drinking all his life) and that he's put back over the years over $2 million for his three kids. He tells me, "oops, I forgot I was supposed to pay for mom, you can sue me, but I'll be dead before you get it, you're screwed". After Mom died, I had to file for bankruptcy because I had loans against my house for Mom's medical bills. (She was in the hospital 3-5 times a year for 10 years and her insurance just didn't cover everything.) I was also the only one paying for her meals, clothing, and all her other expenses. In the twenty years Mom was sick, my brother paid for ONE MEAL - that's it. He never took her to a single doctor's appointment, sat with her in the hospital, paid for her medicine, NOTHING. Instead, he sat at home and drank and smoked and neglected his mother and children. Mom died in 2004 at the age of 85 because I didn't have anything left to charge the treatments against. I was just wondering if I have any legal rights to reclaim half of the expenses Mom had? We all live in Tennessee within 20 miles of each other. I'm not expecting much, I don't want to be paid for my time or care given, nor do I expect him to pay for my lost wages for 10 years, but I would like half of the $200,000 that I spent out of pocket on Mom so my son (whose college fund was also used to help pay Mom's debts) could go to college. Am I being unreasonable in asking for him to finally step up and admit he needs to be held accountable?