Similar to an aura...the spiritual signature. Everyone's differs, but alike entities share certain patterns. It's how I was able to tell that Tybalt wasn't human, more akin to myself but not quite the same. No one has a signature close to mine. Yours is radically different from a human's-think of it like someone playing two different piano pieces in different keys.

[Storm-he doesn't recognize that name.]

Two hearts...that is unusual, but not an impairment in any sense.

...Regardless, yours sound like a happier kind than mine.