Two souls (3.5e Trait)
From D&D Wiki
You were supposed to be a twin, but your twin died before birth and his soul is attached to you. They may aid you by letting you see through their eyes, moving objects, and mind controlling weak-minded individuals.
Benefit: You gain +1 Int, Wis, and Cha but -1 Str, Con, and Dex, as if one age category higher. In addition, you may either use Scry, move an object 5 ft, or use Suggestion on creatures with 5 or lower Int once per day.
Drawback: You're never alone and people may think you're crazy if you speak to your twin in public.
Roleplaying Ideas: Roleplaying a character with this trait can benefit any race or class (It's like having a invisible, untouchable brother or sister that can speak to you telepathically.)