How Do You Keep Your in Laws from Interrupting Parenting?

I would try to find other living arrangements for them. At their age they are not likely to change so you could be dealing with this for years.

ETA: Sorry - missed the part where they are living with you. So you will have to be involved a bit more than I have been.
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Your spouse has to address this. You have couple boundaries - it's up to each side to ensure that if someone is crossing the line, they handle it for their side.

My husband and I went to marriage counseling for this early on. Your in-laws likely won't change. You'll need a unified approach.

My husband spoke with his parents. They denied doing this. Your in laws will likely too.

If my in-laws start up in-front of our children - I remove the children, while my husband deals with his parents.

Essentially it came to this kind of conversation - if you can't respect us, you won't be welcome to visit.

Now, when it happens - my husband just cuts them off. He's become very good at it.

I will add - we've had to take breaks from my in-laws at times. The argumentative thing - we know well. We decided that wasn't healthy to have around our kids.

Boundaries are crucial and your spouse has to stand up to them. Otherwise, it will be very difficult.

Good luck

Welcome to mamapedia, T.!

Your husband needs to shut his parents down. NOW. They are in YOUR home. Not the other way around.

IF they can't respect your rules, they need to find another place to live.

Read Suz T.'s response. Twice.

Now, have your husband say this to them. Emphasize that doing it in front of the children is a deal-breaker.

You can add that they have raised a fine son just the way they wanted to, and you married him because of it. They have to trust that their parenting is done and appreciated.

Moving the in-laws in was a HUGE step that should have had a lot of conversations up front about 'the rules' of living together in a multi-generational setting.
You all need boundaries - you haven't got them - and this is the result.

You and your husband are the alpha pair in your household - or you should be - and you've got issues because you and Hubby are being challenged for the alpha position - and that makes for a lot of confusion for your kids.

You need to have some conversations now - alone with them when the kids are not there - and you need to kindly but firmly tell them
"You've raised your kids - and you are done and have done well.
However it's our turn now to raise our kids as we see fit.
When we want your opinion - we will ask you - but until then you do not argue with us when it comes to our kids.".
And then you establish a code word for when they are over stepping their boundaries which will - in the presence of your kids - let them know when they need to shut it and take a time out.

I'm not sure why they are living with you but maybe you need to get some family therapy to make things work.
Otherwise you might need to consider that they need to move out.

You and your husband MUST sit down and talk about what you BOTH want to do. Then HE needs to sit down with his parents and tell them they are family, but INVITED into your home as guests. it is their job and responsibility to respect your rules and parenting style.

If they can't abide by that? They need to leave. As to allow this to continue will fracture a relationship that you love.

Your husband needs to sit down with them as it's his parents and tell them if they are going to live with you they need to let you parent and they need to back off. If not they need to find different living accommodation

Your husband and you, with him taking the lead in the conversation, need to sit your parents down and explain all of this to them very simply. Tell them that you love them dearly and value their opinion but they simply can not continue to question your parenting, especially in front of the children. Maybe tell them that if they have true concerns they can always come to you both, but not in front of the kids.

Your husband, maybe with you, maybe without, needs to sit his parents down and talk to them. Tell them that this must stop. If they have something to say then say it in private.

Otherwise you are going to need to take your children to their room to discuss things. Door shut. Tell them specifically if they don't do what they're supposed to do then there will be more serious actions on your part.