An almost four. this probably depends on the situation. how well parent and child get along. in my case, it would have been fairly high on emotionally difficult. my mother was very dominering and controlling. it was her way or the highway. she was right and you were wrong. I know if we had faced this situation, it would have been hard because, I would have gone back to being her child and she would be the adult. with my mother you could not dare to have an opinion that was differerent from hers or there was hell to pay. I loved her but there is no way I could see living together. just staying at our home for a few days when she lived out of town was enough to show me how much it would not work out.  guess it depends on each family and how well you get along. In my case it would have been very hard. my dad it may have worked out. my MIL um.. nope  do not think so. Sorry if this makes me look like a jerk.just being honest.  PS. I would not move in with my kids when they get out on their own either.

Me and a sibling nursed a parent who went through a slow death. . .living with us for a few months was tough. . .on the plus side, my in-laws are super-nice to me because they know they will be warehoused in a roach-infested retirement home instead of eating like gods in my house in a few years if they ever get on my nerves. . .

When I was a kid, I had grandparents move in. Lots of stress and strain developes. This used to be common but now we palm the old-folks off to nursing homes.