How can I keep my aunt and uncle from being taken advantage of?

A few years ago a friendly couple moved into my aunt and uncles neighborhood. It started out as just being concerned neighbors , friendly visits, etc. Then every time any of the family visits they always show up. Then they had some stuff get stolen from their garage, I said I was going to get them some new locks...neighbors beat me to it. I mentioned I was going to get her some new curtains.....neighbors did it before I could get to her house. They even offered to move in and take care of them if they would leave the estate to them.they are in the house all ours of the day and night. The entire family is concerned but my aunt just gets mad if we say anything about it. The neighbors even cook for them. Two separate plates....two different meals. My uncle gets one thing and my aunt gets something different. What can we do short of quitting our jobs and being there 24/7. None of us even want to visit anymore because the neighbors always show up and we can't discuss anything without them being present.