Ok, when I bought my large (only about 3K sqft) house, I planned to have my mom move in with (back then) "us" to help with the kids.The house is a one story ranch with an law suite in the walk out basement which is about 1200sqft with separate bathroom and kitchenette. By the time my mom moved in with us there where no more "us" because we got divorced, and the house became mine.
Before my mom's final move in, we did have a few trails with my mom staying with us for a few weeks. Each one of those trails failed and my mom had to leave earlier. However, when my mom did finally move in with me and the kids a bit more than 3 years ago, we have no problems, so it could have been my ex, even though it didn't seem like he was the problem at the trial move-ins. I'm very glad my mom did finally move in, we are all very happy living together, her, me and the kids. And, the funniest part, my mom does not stay in her in law suite because she has bad knees now and getting up and down the stairs isn't an option.
My ex in laws are retired and actually live not too far from me. They voluntarily volunteered to watch the kids when the kids are with my ex. But after some time with the kids being with them for longer periods of time due to Covid and my ex getting night shift job, my in laws got fed up with watching our almost teen kids and practically kicked them out one night. So, now the kids are with me full time. In my state the kids could be left alone and I prefer my kids to cook, do dishes and other household stuff on their own, so I don't really need my mom to live with me, but sometimes it is helpful to have another set of hands around.
So, my bottom line, it's seems to be very individual. Back when we did the move-in trials I was sure that it wouldn't work with my mom and thought that with my in laws it would work (if we needed to move in with them for some reason). But apparently I was wrong. My in laws really like to have their space and my mom doesn't mind not really having her space ( she does have her private room and private bathroom), but we share one large kitchen and the fridge, and actually we split the grocery bill. She doesn't drive, so I take her everywhere she needs to go. And, just a side note, I do not charge her rent or utiities. Her pension is really small and I want her to have money to buy things for herself and presents for our birthdays, Xmas and such. Plus, since she doesn't use her in law suite, I Airbnb it. I can share that the meal preparation works like this, my mom cooks for herself and me and I cook for me, the kids and my mom, and the kids cook for themselves. My kids are very picky and are used to eat more unhealthier food, while my mom and I eat more healthier. Since the kids are very far from being overweight, I do not worry about their eating habits, it will grow on them eventually. We also have 4 cats, one for each one of us, so it might be the cats help us not to stress out too much (just a side note, my in-laws are allergic to cats). Also, I think it's important to consider recreation. In my case, since only one adult is driving, it was important to live in a safe area, so my mom and the kids can take walks. Plus, we live in walking distance to coffee and other shops, vet clinic, restaurants, convenient shops, and the school. So, they don't really depend on me. We also have art exhibits, concerts and other things in walking distance and before Covid we loved going there, the kids often went with their friends and I went with my mom.