Could this be Rainbow Dash's sister?

[Blaze Ishtar 2]

So, in Season 8, Episode 4, there's a character who's been dubbed, Valley Glamour, who plays a semi-important role to the plot of the episode. She hasn't really gotten a lot of attention, but I have theory posted on DeviantArt on who she may be. I actually think she's Rainbow Dash's sister. This is her right here:

 

Here's a link to my theory if you want to know why I think this: https://serious-sam-64-64.deviantart.com/journal/Theory-Valley-Glamour-is-Rainbow-Dash-s-sister-747481993

Edited May 31, 2018 by Blaze Ishtar

[Megas 27,065]

No, Rainbow Dash doesn’t have a sister, it’s more or less confirmed that she’s an only child... not to mention there’d be some real bad favoritism in her family 

[DonMaguz 1,023]

Doubtful, Dash's personality yells 'only child' and pony colors and styles mean next to nothing when it comes to family members.

[SDP40F amtrak 2,442]

I don't think so but she have different color than rainbow dash 

[Blaze Ishtar 2]

2 hours ago, Whomps said:

No, Rainbow Dash doesn’t have a sister, it’s more or less confirmed that she’s an only child... not to mention there’d be some real bad favoritism in her family 

Hm, yes, it's most likely she is the only child in the family. And that's something I mentioned in my journal on DA, is how maybe her parents focused on RD for so long that Valley hasn't appeared in many photos. But if you doubt my theory, that's fine with me, I just wanted to see what other people think.

[FlareGun45 2,221]

She needs to stay an only child to have her relationship with Scoots more needed from her side! Besides, someone from the Mane 6 needs to be an only child! The others all have siblings!

[Thrond 3,257]

If Rainbow Dash had any siblings, we'd know about them. The show has given every indication that she's an only child. 

[Lunar Glow 674]

Honestly, as far as the show goes, I'm sure Rainbow Dash is an only child especially after the "Parental Guidance" episode. But if there was any possible chance of Rainbow Dash having a sibling, I would think it would be Daring Do or an adopted Scootaloo.