They handle their families separately

Each person manages their own parents, their own siblings, their own complicated family conversations. The difficult mother-in-law gets handled by her own child. The brother's financial situation gets navigated by the person whose brother it is. Long-lasting couples operate on an implicit principle: don't inherit each other's wars. Outsourcing your difficult family member to your partner — asking them to manage the conversation, carry the frustration, or serve as the buffer — is one of the slowest leaks in modern relationships. This isn't about keeping families separate in all ways — it's about not turning family friction into shared emotional labor that the partnership wasn't designed to carry. When a partner consistently has to manage both their own family and yours, they become a de facto emotional employee rather than a companion. The clarity that comes from each person handling their own is protective. It keeps the partnership from being drafted into conflicts it didn't create and can't fully resolve.