For the most part, readers seemed to side with the original poster.
“Wow, your parents are spoiled. A rent-free, up-to-code apartment sounds pretty sweet. If it isn’t good enough for them, then they can make other arrangements. But if you let them into your main house-it will become their house. And you won’t be able to get away from them. NTA.”
“NTA. If it’s a converted guest house that’s completely up to code, I don’t see a reason that they would want to go into the house as everything you have in the house you have in the guest house too. My friend recently turned her shed into a beautiful guest house, with kitchen appliances, a private bathroom the works. Her parents are currently living there, and they don’t have a problem with it. They like the privacy, and they like being close to their child.”
“They wanted into the main house for you to be their cook, maid, and carer. In the guest house, they have to fend for themselves.”