The fairly obvious answer is: This belongs in the forums, you duck.

@Trickquestion  
@NostalgiaSchmaltz  
@Thanotos Omega  
It makes as much sense as having the ruling powers of Equestria designated as “princess”, while there are other princesses who obviously don’t have that much power.
 
@LanceOmikron  
Pretty much this, yes.

@PonyPon
 
Exactly. Blueblood would make a perfect gazpacho.

Correction: I’m a strong supporter of the “Luna’s biological son” thing.

@Starswirl  
Or that one episode of Chowder.

@Bronitarian  
So insanity, basically?

@Starswirl
 
Jealousy over not being the most important person in canterlot. He eventually kicks everyone out, after goes eviction crazy. He thsn sees himself in a mirror and banishes himself, only realizing what he’s done after he gets thrown on his ass.

@Bronitarian  
Unless he was brainwashed by Chrysalis, why would he do that?

Same deal as Cadance. Celestia adopted him under her sister’s name.

@Starswirl  
That just makes me think there might be an episode where blueblood tries to kick celestia out of canterlot.

@Bronitarian  
Hmmm- how about this: Canterlot. Yes princess Celestia resides there, but she only does so after her original residence was destroyed in the fight with her sister.
 
So he’s the Duke of Canterlot, but she outranks him as Grand Princess. Nevermind that she’s been there for so Long barely anypony remembers it’s not actually her Holding.

you know in several older cultures,(such as japan) just as it was not completely unheard of for a low ranked citizen to be officially ‘adopted’ into a noble family various reasons, it was also not completely unheard of for a noble to be ‘adopted’ into a royal family line

He should have been named count blueblood, has a better ring than prince or duke.
 
But this does raise a different question. Where, exactly, is blueblood’s domain? As in, what part of equestria does he rule?

If Discord were here, Chaos would be at an all time high.

@Jadefire  
But but if we don’t argue about asinine crap like this we will start to remember how long it is until season 4 do YOU want to be the one responsible for flooding the site with “Let’s take season 4 and move it to today” that would mean Sponge Bob references those would remind us how none of our favorite nicktoons are still on and how far gone our childhoods are why do hate our childhoods?

There are two possibilities, and either one makes Celestia his great-to-the-nth-aunt. Celestia might have (ostensibly) married the childless king of Unicornia, making his sibling’s line the heir and Celestia their aunt. Otherwise, one of the sisters did have a child at some point and she is still the (great-great-whatever) aunt of their descendants.

@Trickquestion  
(shrugs)

@Sjogre
 
@Background Pony
 
The whole “Mother’s side” thing implies that Blueblood is Celestia’s distant cousin, not nephew.

@Trickquestion  
Simple: Ask Blue’s parents to adopt her.
 
Why would they say no?

@Background Pony  
How do you adopt someone as your niece? Isn’t the whole point of adoption that you make them your child? I mean, it fits with Celestia’s character, but I can’t say I’ve ever heard of something like that anywhere else.

@Jadefire  
THANK YOU. WHAT THIS GUY SAID.

@Thanotos Omega  
Much like the show itself. The book series mentions that Cadence was adopted as Celestia’s niece, so maybe it’s the same thing for Blueblood? Who knows, and who cares.

Lauren Faust explained it that he was “their nephew 27 times removed on Celestia (and Luna’s) mother’s side”. Meaning their mother had a sibling who had children, and Blueblood is a distant descendent of said children.
 
Lauren Faust confirmed that Celestia and Luna don’t have any children (unless, of course, the show directors decide otherwise in a later season).
 
Now can we put this damn debate to bed already?

@Background Pony  
That like is not 100% cannon and still makes little since

Lauren once mentioned that he was many times removed on Celestia’s and Luna’s mother’s side, so that indicates to me personally that he’s a descendant of one of Tia’s and Luna’s maternal aunts or uncles, as opposed to an unseen sibling (since, if it was Celestia’s other sibling, the comment about Blueblood being on their mother’s side would be moot. Unless it was a half sibling, but that opens up a whole new can of worms).
 
Technically that would make him a cousin, not a nephew, but “nephew” is probably easier an easier concept for the kids to grasp. That, and things change during writing.
 
Blueblood being a nephew isn’t the truth, but it’s a lie you can understand.
 
@gittonsxv
 
Well, there IS actually precedent for Celestia having an adopted niece: Cadance. Blueblood being an adopted nephew would certainly simplify things.
 
@Blood
 
Either that, or he needs to get the sort of character development that he gets in fics like The Best Night Ever and The Flight Of The Alicorn.