Your SD needs to move out.

As one example, if I’ve always seen my bedroom as private space where children shouldn’t enter, but the family I’m joining has always had an “open door policy” where kids are encouraged to come in any time, those expectations are going to clash. I want my bedroom to myself, and I say so. This doesn’t make intuitive sense to the kids (or their parents), so the kids have a hard time internalizing this expectation and the parents often forget that I’m “weird” in this way, or resist enforcing a rule they don’t understand. I keep reminding, it rarely “sticks” and we’re increasingly frustrated. If we’re not careful, I may develop a story that the kids are disrespectful and the parents rude. Meanwhile, the parents may think I’m unreasonable and don’t want to bond with their kids. My partner wants everyone to get along and is confused about how their loved ones could have come up with such uncharitable stories about each other.

Neither approach to bedroom usage is “right,” but the other’s approach will feel foreign, even gut-level “wrong,” because one’s own approach feels so comfortable and correct. Feeling comfortable feels good, especially in one’s own home and with one’s partner. We do have the option, though, to look for areas of discomfort that we’re willing to adapt to and be flexible around on our end, recognizing that others may be trying/struggling to do the same for us.

After all that, it can also help to explicitly recognize the positive side of the behaviors, and draw clear contrasts without judgment for new behaviors. Something (genuine) like: “I love how comfortable you all are together, and how you like to be together and encourage the kids to be independent around the house too. I’m enjoying learning about you and spending time with you. We all have things that we like different ways, and one thing I’ve realized is that my family always kept the bedroom aside as a “space for grown ups.” I know that would be new for the kids, but I think they’re quicker to adjust than I might be;). Could we brainstorm ideas for setting up different expectations for my room compared to other places they go? (If yes) Are there spaces at home or school that they know are only for grown ups? (If yes), Great, so I’d like to let them know that going into the bedroom at X, Y, and Z’s house is fine, but for some people like me, this room is more like the office, so let’s use office rules here instead.”

The STATE process seems like a great way to gather and share this data, discuss differences openly, and see how a new family dynamic can take shape. Best of luck.