Start with the decision or moment that affected you, not a verdict on your partner's family. You may need agreement before hosting, a response to personal comments, privacy around your plans, or a fairer holiday schedule. Those are specific conversations. “Your family controls everything” is much harder to turn into a workable plan.
Identify which boundary belongs to whom
You can decide what personal details you are comfortable sharing. A shared home requires discussion about guests and hosting. Your partner can still have their own relationships and seek support outside the couple. A privacy request should not become a ban on talking to anyone else.
Write the actual issue in ordinary language: “I found out about overnight guests after the invitation was accepted.” That gives you a decision process to discuss, rather than a contest over whose family matters more.
Agree before either person answers
Try: “Before we confirm the visit, can we agree on dates, length, and who is handling the hosting work?” For holidays: “Both families are expecting us, and we haven't chosen our own plan. Let's decide before replying.”
Put travel, work, disability, rest, money, and care needs into the conversation. An arrangement can look equal in hours while requiring very different effort. You do not need to solve every future holiday; agree on this one and a way to revisit it.
Ask for specific backup
If a relative makes a personal remark, explain what support would have helped: “When that joke was made, I felt alone. Next time, could you change the subject or say that topic isn't up for jokes?”
Your partner may not know whether you want a public response, a private follow-up, or help leaving. Talk about those choices when possible. Do not assume the only proof of support is a dramatic confrontation.
Prepare one repeatable sentence
For questions about children: “We'll share news when we choose to. Let's talk about something else.”
For an invitation you cannot answer yet: “We need to check our plans and will get back to you tomorrow.”
For a shorter visit: “We can join for lunch, but we're not staying overnight this time.”
The sentence should reflect an agreement, not falsely speak for both people. If you disagree with your partner, resolve that privately where safe rather than announce a joint answer you have not reached.
Keep support separate from oversharing
Someone may need advice from a friend, relative, or professional. You can discuss the use of identifiable screenshots and private details without forbidding support. “Please don't forward our private messages” is different from “You must never tell anyone what happens here.”
Safety disclosures, documentation of abuse, and access to help should not be restricted by a household privacy agreement.
Plan for the practical work
Family boundaries are not only words. Who tells the relatives? Who books travel? Who cleans and cooks? Who handles the follow-up if plans change? A boundary that leaves all the organizing and emotional labor with one person may not solve the original issue.
Consider a shorter visit or separate arrangements when they are feasible and freely chosen. They are options, not punishments. Maintain space for each person to care about their family without giving either family automatic control over shared commitments.