We had this with my mil and my husband’s brother.
He was horrid to his mother, and would always side with his father, even though my fil and mil were always so very much in love, he just didn’t get on with his mother, she was a difficult woman with everyone only doted on my fil, and then my husband
Soooo, when fil died he left everything to my mil, with but they had an understanding that everything would be split 50/50 when she passed with the 2 sons. I should mention they were very comfortable off.
Move forward 6 or so years, bil has very little if any contact with his mother. We have total care of her, and thought she still lived on her own. She did need our constant attention, she had care staff go in every day, but we needed to speak to her twice a day and do shopping etc, and as she lived 40 miles away that wasn’t easy, but we did it, me for my husband not for her but still. Then the accident, and after a long hospital stay she went into a care home, we sold her house and used her savings to pay for this. My bil was kept informed the whole time but made it clear he wasn’t interested. When she was dying we told him, nothing, he hadn’t seen her or contacted her know for over 3 years .
Her will - she left 25% to my bil and 75% to my husband. It took a lot of convincing to get her todo this she wanted to leave 100% to my husband. We convinced her in the end that fil wanted to split 50/50 and she should respect his wishes. So she decided to leave her son 50% of her husband’s half of the estate. He kicked up a storm at first, didn’t even attend her funeral, then all of a sudden the solicitor contacted to say he had agreed to it. Needless to say we haven’t heard from him since.