My boyfriend (34M) and I (30F) are planning to get engaged soon. We don’t live together yet, but we plan to in the near future. We've been together for a year and a half now.
He’s very close with his younger sister (28F), which I’ve always respected. But we’ve been running into disagreements about boundaries, and I’m trying to figure out if I’m being unreasonable or if this is something we should seriously address before getting engaged.
He wants to occasionally spend the night at her apartment. On its own, I know that might sound harmless—but there’s more context that’s making me uncomfortable:
They’ve done things like make each other breakfast in bed for birthdays
He took her out to dinner on Valentine’s Day this year (we celebrated the night before because I had to work)
He had talked about keeping clothes at her place so he could spend weekends there more easily (he’s since agreed not to do that)
When we first started dating, he and his sister were actively looking to buy a house together and live together. Even after he and I became official, he was still house-hunting with her
That last part is what really stuck with me. At the time, when I questioned how that fit with him saying he wanted a wife, he told me it wasn’t really different from them already living together at their parents’ house. Now he says part of the reason they didn’t move forward was because he was getting serious with me—but that wasn’t clearly communicated to me at the time.
Because of all this, overnight stays don’t feel like just “visiting family” to me—it feels like an ongoing level of closeness and planning that overlaps with what I would expect in a primary partnership.
I told him I’m completely fine with him spending full days with her, even late into the evening, but I’d prefer that he comes home to sleep. To me, that boundary reflects prioritizing our relationship as we move toward living together and building a life as a couple.
He thinks I’m being unreasonable and says it’s just normal sibling closeness. He also told me I’m being “rigid” and “limiting his freedom” by having an issue with overnights. He says that once we’re married and living together, he naturally won’t be staying over there anyway.
I’m not trying to come between him and his family, but I also don’t want to ignore something that genuinely feels off to me—especially this close to engagement.
Am I overthinking this, or are these valid concerns about boundaries, communication, and long-term compatibility?
TL;DR: My boyfriend wants to occasionally sleep over at his sister’s place, but given their very close dynamic (breakfast in bed, Valentine’s dinner, previously planning to buy a house together), it feels like blurred boundaries to me as we’re heading toward engagement. He thinks it’s normal and I’m overreacting.