To Paradise by Hanya Yanagihara
Hanya Yanagihara's book spans approximately 200 years, with characters entwined by a Washington Square townhouse in the years 1893, 1993, and 2093. It meets your criteria of multi-year relationship-driven sagas. Across time, Yanagihara presents an alternative history of America where racism is still rampant but queer partnerships are completely acceptable.
There have been plenty of reviews that unpack the characters, historical referents, and storylines of "To Paradise," but one thing that is often overlooked is the profound adoration that Yanagihara has for objects. Each item is so intricately cataloged and described that they become characters, witnesses, and naturally, carriers of the long span of time covered by the book. It's gorgeous, sad, and complex.
(Also, I'm realizing that "Paradise," is becoming a theme in my feed. I think it is hard to grasp what paradise or sanctuary might look like and I appreciate when thoughtful writers grapple with the idea.)
