What do you do when the family of your in-law with Alzheimer's won't put them in a facility because they feel guilty?

I am so sorry to hear about the Alzheimer's. Is the current family you are speaking of not taking good care of him/her with the Alzheimer's? Does the person with Alzheimer's live alone and a threat to him/herself?
If the family feels guilty about sending the loved one away, maybe it's because the person is still in a state that is somewhat manageable, and they would rather care for this person instead of having strangers do it. They may also fear that this person would get very depressed and lonely around strangers in a facility, so are holding off - I am sure that you know all this already, but it is so difficult to give your loved one away when there are so many unknowns at facilities nowadays. Good luck with this.