Couplecore: Indie rock centered on a romantic pair.
From the New York Times pop music listings, April 17, 2009:
THE ROSEBUDS (Sunday) It’s been called “couplecore”: indie-rock bands centered on a romantic pair. Over nostalgic synth-pop, Ivan Howard and Kelly Crisp of the Rosebuds mix mushy sentiments with thoughts about adult responsibilities and the long challenge of staying happy together.
The -core suffix comes from the vocabulary of movies (hardcore, softcore); it recently spawned mumblecore. It has migrated successfully to music, thanks to the naming of genres such as "hardcore punk." In addition to couplecore, see nerdcore, metalcore, and grindcore.