How can I get rid of my mother's husband?

As they approach 80, he has made her life miserable. He was never smart, considerate, or romantic - she had t forgo all of that since they were married. Now with the onset of dementia and advanced prostate cancer (that he refuses to get treated for despite having all the healthcare in the world with his veterans benefits), he is more stupid than ever. What is worse is that he is not man enough to even fight it for the sake of his wife - if not for himself. He is lazy, rude, uncultured, and embarrassing in public. He routinely blows off birthdays, anniversaries and Valentines Day. Only our family even gives a shit what happens to him as his brother, sister, and 4 sons could not care less until they need money. If it wasn't for us, he wouldn't get anything for Christmas every year. He has the temperament and the intelligence of an 8 year old - literally. He stresses my mother so much that I am worried for her health and happiness with the golden years that she has left. He needs to be in a managed facility of some kind because is an classless idiot but I know that she lacks the resolve to leave him. For her sake, I have to get rid of him somehow.