@redweasel  
She has a thing for rainbows

rainbow blaze was windy whistles’ first husband.

@Background Pony #4452  
Maybe he left home for the same reason Dash did.

@Background Pony #4452  
Eh, I’d prefer it if Dash were an only child. All of the other Mane Six have siblings already. Plus, it would make more sense given how her parents act.

@Background Pony #4452  
Bow Hothoof: Rainbow Blaze, best son ever! Rainbow Blaze! Rainbow Blaze! Rainbow Blaze!

@LanceOmikron  
I go with Blaze being Hothoof’s son, and Dash’s brother.

@SeraphimDawn  
£5 saying its uncle

@Spoonlol  
Dibs on cousin.

I like the idea that he’s Dash’s Uncle and mentor/trainer

or he the brother of bow hothoof

big brother?

maybe a cousin?

ponies wearing clothes is weird

@Macaroni C-Pony
 
Hothoof has a narrow urethra and it was a miracle RD was born in the first place.

@TexasUberAlles  
The line starts behind Pinkie.

I know if I had been born first I would have been an only child.

@LanceOmikron  
I could imagine Rainbow desperately wanting a little brother, and her parents not able to conceive anymore.
 
Years later, she meets Scootaloo…

@LanceOmikron  
There’s really no evidence against Rainbow Dash being an only child.
 
Maybe they smother Rainbow because Windy caught something or whatever and couldn’t have any more children.

@Landmark520  
So his appearance in “A Hearth’s Warming Tale” was his ghost?

Rainbow Blaze was RD’s older brother who was in the military, when RD was very young he went to war and was killed in action. As a result her devastated parents clinged to Dash and showered her with unconditional love and praise because they never really got over the trauma of losing their first child.

@animefan14  
IKR, check out Shining Armor from when Twilight wad a filly, all the way to when Cadance was pregnant.
 
And BigMac applies too, he was kinda snall when Applejack was a filly

@Background is Best Pony
 
Well you, habitatunholycity, and TexasUberAlles all pretty much confirmed the same thing I commented about, as well as Macaroni saw it too. I’m glad that there are a bunch that picked up on it, and you definitely have a point on letting himself go. Considering how much of a filly RD was in those flashbacks compared to now, definitely wouldn’t be surprised if he’s a bit like Mr. Shy when he mentioned in “Flutter Brutter” that he had retired from the cloud factory. Damn, he’s definitely middle age at least.

@habitantunholycity  
Blaze also appeared in that hearthswarming episode that Starlight was in.

Everybody seems to ignore that Blaze there appears when RD is a filly. They’re likely the same pony, and Hothoof just really let himself go.

It’s the same dude, dudes; he just looks different because Big Jim has slept once or twice since Season 3, nothing else needs to be attached to the matter.