It's hard to pinpoint one specific original song for a Christmas love story. Different artists and composers might have created their own versions. You might have better luck looking through Christmas music compilations or checking with music critics' reviews.
Honestly, there's no single definite original song. It depends on various factors like the context or the particular story. You could try browsing through Christmas music albums or asking on social media groups dedicated to Christmas music.
I'm not sure exactly. There could be many different songs written specifically for Christmas love stories. Maybe you could search on music streaming platforms or ask on dedicated music forums.