Artemis isn't the only goddess out there with a twin brother. Believe us, sometimes having a boy for a twin isn't easy, especially when he's as popular as Apollo. It's easy to get overshadowed. Sometimes you need some other goddesses around to let off some steam.
Just like Artemis, the Norse goddess Freyja is the twin sister to a male god of light (Frey). That's about where Freyja and Artemis' similarities end, though. While Artemis is a permanent virgin, Freyja is a fertility goddess. Freyja is more like Aphrodite in that she really gets around.
This Aztec goddess' twin brother is named Xochipilli, who, like Apollo, is a god of art and music. Artemis may be cool, but Freyja and Xochiquetzal just click, since they're both in the Prom Queen clique.