I got a package today from a small business. The owners/founders are sisters whose names both start with C and are rendered as one syllable.

One of the sisters has an unusual spelling that I've never seen before, of a name that I've seen on both genders.

Guesses?

Edit: I'm going to rewrite the hints so it's easier to read.

Both: Start with C Single syllable

Sister 1: Common nickname for several legal names, less commonly a legal name: Cat

Sister 2: Gender neutral to masculine name. Highly unusual spelling, but very common name. I know several people with this name or have this nickname for a longer variant. Chrys

Guess as much as you want!