Can my brother-in-law sue me and my husband?

I really don't know where to begin. My husband and I took care of his mother and brother for well over 2 and 1/2 years. Their younger brother had stage 4 stomach and esophagus cancer. Mother now has dementia with delusions. For the 2 and 1/2 years I cooked their meals, took her to the doctors, feed both of them did their laundry, cleaned their house made appointments, picked up their medication. You name it, my husband and I did it for both of them while caring for our own family. We even feed their dog and brought him to the vet and bought his food, wee wee pads and treats. We sat in the hospital from morning to night days at a time. Well before their mother was diagnosed with dementia, she asked me to be on her bank account and she even called the bank, but I said no. I didn't feel right and most of all, I didn't want to get accused of any wrong doing. So, she said she would then put my husband on her accounts and to open up credit cards so he could take care of the home, etc. She put me on her credit card, when I received it I called the credit card company and immediately had myself removed (oh no, not getting involved in a family affair ). So, during this time while she was in the beginning stages of dementia, my husband and I went to the Alzheimer's meetings and called elder attorneys, nursing homes, her doctor even out me as her health proxy. She was going outside all hours and days and talking to her invisible people, knocking on neighbors doors and saying her husband needed money when her husband has been dead for 13 years. At this time she was dressed in a robe, and her shisu and a big stick. It was 5:45 am. Another time shes outside in the neighbors yard in 3 feet of snow, no shoes, no coat and a huge dog was inside the house barking like crazy. My husband and I take her out because she had no idea how she got in. We asked what what she doing there. Her answer was she was helping the girl get over the fence, she would take her clothes off and go outside. It was time for her to be placed. Finally, I call every place you could think of and Medicare said they would pay 100 days in a nursing home. I have been trying to get Medicaid for well over 2 years. Finally APS and a nurse came to her home. Of course, I was there everyday from 7 am until 5. Then my husband would do the next shift, 5 until morning. This went on everyday since the son with cancer passed away. Finally, I found a nursing home close to where we could get there daily, sometimes twice a day. The nurse from the nursing home came to my mother-in-law's home, did a intake and called back shortly later and said to bring her in. I asked what about payment, she stated they would take care of all of the paperwork. Thank god! I am drained mentally and physically, since I had invasive cancer and graves disease myself, and needed rest that I was not getting. Anyways, my husband and I brought her to the nursing home. She cursed us out all the way there, including there. Got to love her (lol).....We know it's dementia and she had no control. She also was physical. Well, my husband tried to get POA and was told it was too late because she had dementia. Nobody never mentioned there was such a thing as guardianship. I didn't want it, but I am sure my husband would have. He walked miles to get to her in the cold wet snow. Ok here we go, the prince and shining armour (the long lost ranger ) came into the picture, literally threatening my husband and I that she better have all her money in the bank, the house better be kept up. He said the nursing home contacted him. He went to Supreme Court and is getting guardianship. I know my mother-in-law if she was in her right state of mind. She would not want him to have guardianship. He is threatening to sue my husband and I over money my husband has used for her and her home. As I stated to the brother, sue me for what, for being there for your mother when you weren't ....( sorry I had enough of this guy), and I am on absolutely nothing of this woman's. I have been there because I love my husband and her. She always said, she wished she could pay me. I told her I would never accept money from her and I never have. So, can this brother sue my husband and myself  for money from her account? I am not on her credit cards, nor her bank accounts. I refused, thank God! However, she put my husband on her account before dementia. The "brother" we phoned when his father passed he did not go to the services or the funeral. His daughter phoned him and asked him to come. His response was don't hold your breath.....( smh )...This guy is going straight to h*ll with no exit....Then we phoned him and told him his brother had cancer (no response)....We called and told him his mother has dementia (no response)..We phoned him and told him his younger brother passed, again (no response from him on the telephone) and again no entrance to any of his brothers services or funeral. His brother died on the floor again my husband and I called and made arrangements