I've heard she's Celestia's niece? What other sister does Celestia have besides Luna? I could be wrong about this but just makes me wonder about where she came from lol.

Here is a link to the wiki: http://mlp.wikia.com/wiki/Princess_Cadance

It kinda makes sense that its her niece only because she gave her a royal wedding. However I'm wondering about her having another sibling also. Idk maybe they will fill in the gaps later.

I though this was quite interesting, "Lauren Faust was involved in the inception of the story in which a Princess named Cadance appears. At that point in development, she was not designed as an alicorn, and Faust was surprised to see her as such; the decision was made after she was no longer working on the show.[4] Faust intended Princess Celestia and Princess Luna to be the only alicorns.[5]"

Doesnt she also have a nephew? The prince Rarity chased after in the Gala episode.

Prince bluebird? I don't believe it ever mentions him as being a nephew.

Yep! He is! It mentions it in the Ticket Master. I wonder if he's Cadence's brother.

Oh wow I remember that now Rarity mentioned that in the Show. XD

I do need to rewatch it then XD