My brother-in-law has had an accident, and an elder sister-in-law is like a mother. Isn't it only natural for you to take care of his two children?

(From a reader submission, images in this article are from the internet)
My brother-in-law has had an accident, and an elder sister-in-law is like a mother. Isn't it only natural for you to take care of his two children?
Before I got married, I always thought marriage was just a matter between two people. However, after getting married, I learned that this is not the case at all. Everything that happens in the whole family affects my personal life. More importantly, no matter how hard I try, my in-laws never appreciate my hard work and sacrifices, which makes me deeply miserable.
In fact, from the very beginning of my marriage, my in-laws' way of thinking was something I could not accept. They believed that since I had married into this family, I was one of them, and I had the responsibility and obligation to take on everything in the household. Although I felt quite dissatisfied about this, for the sake of my husband's face, I still chose to silently endure it. So, as the elder sister-in-law in the family, I took on all the housework. Not only did I have to go to work as normal, but I also had to buy groceries, cook, do laundry and sweep the floor. I was busy from morning till night. Although I secretly complained to my husband about my dissatisfaction, his attitude was exactly the same as his family's. He thought everything I did for the family was only natural. Seeing my husband's attitude, my heart was full of grievance and resentment. I thought to myself, if it were not for my young child, I would definitely divorce him and get away from this cold-hearted family as soon as possible.
However, misfortunes never come singly. Just when I was overwhelmed by the burden, my younger brother-in-law suddenly had a car accident on his way to work. After all-out emergency treatment at the hospital, although his life was saved, he was left paralyzed in a hospital bed, a vegetative person who was completely unconscious. Seeing that there was no hope of recovery for my younger brother-in-law, my sister-in-law filed for divorce with the court. At first, my in-laws tried every possible way to save this marriage in name only, even using my younger brother-in-law's two children as leverage, all in an attempt to keep my sister-in-law. But my sister-in-law had already made up her mind to divorce, and with her repeated insistence, the court ultimately granted the divorce.
Because my younger brother-in-law now has no ability to raise them, after the divorce, my sister-in-law planned to take their two children with her. However, my in-laws had a different idea. They believed the two children were my younger brother-in-law's flesh and blood, and absolutely could not let my sister-in-law take them away. But to keep these two children, someone would have to take care of their daily needs. However, apart from me and my mother-in-law, the two women in the family, everyone else was a man. In addition, my mother-in-law was already very old and her health was not good either. So the whole family wanted to push this responsibility onto me.
After seeing this situation, I refused outright, because I had my own difficulties too. During the day I not only had to go to work to earn money, but I also had to take care of the whole family's daily life, and in my spare time I even had to go to the hospital to look after my younger brother-in-law. If I were also made to take care of two mischievous children, I would simply be exhausted to death. However, after hearing my refusal, my in-laws immediately showed their displeasure. My husband even accused me, saying, my brother-in-law has had an accident, and an elder sister-in-law is like a mother. Isn't it only natural for you to take care of his two children? After hearing these words from my husband, my heart was full of grievance. You keep saying you treat me as one of the family and always make me give to this family, yet you have never considered how hard I work. Friends, do you think my in-laws' behavior is right?