I’d only do this if my house was physically gone and even then I’m not sure.. and I say this about both my parents and my in-laws.
First, old people can get cranky and nasty when they have health problems. I want to be able to leave when I need to, and more importantly have my kids leave when needed. These health problems won’t be sweet grandma sitting quietly in a chair, I can guarantee that.
Second, your marriage dynamics will change. You may be less willing to be as openly affectionate with your spouse or talk/joke about things in front of the parents. Do you want that? Your parents will know how your marriage is going for better or worse. If you and your husband have a real good night in bed and wake up glowing, they’ll know. If you and your husband have a knock-down fight, they’ll know. Again, do you want that? I don’t, and my family is open about sex?
How old are the kids? What happens if they develop interests the older folks disapprove of, healthy appropriate interests but interests that grandpa or grandma don’t think “are right for a girl” or “right for a boy”? My dad was very much against having our daughter do karate, now he’s proud of her. He also wanted our other kid to “keep going with band” when the band program at the kid’s school literally had her in tears. His response was “make her stick with it”, mine was “she shouldn’t be coming home in tears after each and every band practice” so that was the end of band. We could have had some nasty fights over all these issues. We didn’t I think because we don’t live together. What about if your kids want a pet, and you want a pet but Grandma doesn’t?
What about when an appliance breaks down? Our washer broke during covid. I was literally in tears over it. My husband thought my dad could comfort me and so he had me talk to my dad. My dad told me to “be ready, there are shortages” and that got me thinking. I went to Lowes and had a washer delivered the next day. When I told my dad, he got real quiet and said “I didn’t think that could happen, I was so sure it couldn’t be done, I’m real proud of you”.
What about money and how it’s spent or not spent? My parents didn’t believe in having an hvac contract for years and years, they told us we were throwing money away.. until their hvac broke and the only way to get a competent person to fix it was to sign a contract with a company. Now they love their contractor and praise him on Facebook.
What about if they have or acquire friends you don’t like? My parents have a friend I won’t allow near my kids, and I’ve told my husband “We won’t fight, we’ll just leave” if this person shows up when we happen to be there. For adults who are smart kind people, they are idiots around this friend, and they can do that, just as I can leave when needed.
What if your kids want a pet, and you agree? My mom doesn’t want dogs around the grandkids since one of my kids was bitten by a dog when she was little. That same kid begged us for a dog and happily sleeps with him in bed every night. My mom likes the dog, I don’t think she’d have agreed to us getting him if she had a say in the matter which she didn’t because we don’t live there.
What if something happens that makes you rethink how you and your husband want to do life. My husband worked in a scif for a time. Then I had a miscarriage and I couldn’t deal with the scif anymore. I finally convinced him to work from home or semiremote which he did. My parents wouldn’t have understood that, they worked in offices their entire careers, they also had a baby die, they simply aren’t able to grasp why our loss impacted me in the way it did, and some of this is generational, nobody worked from home in the 1970’s, you simply couldn’t have had that discussion when they lost their baby. I certainly wouldn’t have wanted to have these discussions around my parents, they were too emotional and raw.
What about the house when the in-laws die or sell it? Will you get it and will that cause a fight between siblings? Think very carefully here, grief and houses are a real bad mix.. add in some sibling fights that never really got resolved and it will get ugly.
Good luck, op. I’d not do this, partly because I don’t like the location where both my parents and in-laws live, partly because I like my parents and in-laws and I don’t want to be up close and personal with them on the daily, nor do I want them up close and personal with me.