Elena and Marcus aren't actually characters from the 'Twilight' saga, but I think you might be mixing them up with other names! The series has such a huge cast that it's easy to get tangled in the vampire lore. If you meant 'Alice' and 'Jasper,' they're two of my favorite members of the Cullen family—Alice with her bubbly personality and precognitive visions, Jasper with his brooding aura and empathy manipulation. Their backstories are wild; Alice was turned by a vampire who saw her potential, and Jasper literally fought in vampire wars. The depth of side characters in 'Twilight' is low-key underrated.
Now, if you were thinking of 'Aro' and 'Marcus' from the Volturi, that's a different vibe. Marcus is the melancholic, almost detached leader who lost his mate centuries ago, while Aro is the scheming, power-hungry face of the Volturi. Their dynamic is fascinating because Marcus barely cares about ruling, while Aro thrives on control. Maybe their names just got swapped in your memory? Either way, 'Twilight' has no shortage of dramatic, tragic figures lurking in the shadows.