Rarity could be older yet childlike due to not having much of a childhood, like you said. That’s probably why she stays away from her parents. She wasn’t very affectionate towards them.

@Advance  
Compared to who? The one who is scared of her own shadow, the jock, the party animal, or the spergelord?
 
AJ might be more mature than her but even then I’m skeptical since AJ has a tendency to seek rather childish solutions to her problems whereas Rarity is the most likely to realize that she’s wrong before it blows up in her face too badly.

@NightJack
 
It was said that she hasn’t been able to attend the Gala before, not that they weren’t picked.
 
Also, in the first season alone 3 celebrities had visited her shop, and I kinda doubt that happens at the beginning of one’s business.

@Advance
 
Yeah, she’s bit of drama queen, but she’s still mature enough to own a business.

Rarity could be young because in Cutie Mark Chronicles she shows that she knows how to make dresses prior to getting her cutie mark, meaning that she curtailed her childhood to some extent to get a jump on her business.
 
I dont see her as old because she can still be immature and naive like the others but at the same time it could just be her inner child acting out for the aforementioned reasons.
 
Also, the thing I took away from Sweet&Elite is that the crowds Rarity most wants to impress are rather unfair and arbitrary.  
So that could explain her status as an unknown.  
In ADaPS Sapphire Shores said Clotheshorse magazine called her “an up and comer” or something so there ya go.
 
Or maybe the writers are a tad lazy on this sort of thing

Precisely. She’s been doing this thing for a while.
 
I keep forgetting that Sweetie Belle doesn’t live with her. Introducing her parents created more problems than solutions, I feel like it hindered the strength of her character. She’s still fiercely independent, though.

In all actuality, Rarity isn’t all that mature. Sure, she acts high class and fancy, but she’s also the second most eccentric of the mane six. She often goes into “drama mode” before correcting herself, so she’s really not all that mature, she just acts like she is in order to maintain her high-class appearance.

she still wasn’t

@Dumb Rock  
But wasn’t it pointed out she silly wasn’t known, more that she designed them just in case?

Ticket Master:
 
Rarity:… I design ensembles for the gala every year…
 
I think it’s safe to say her business isn’t recent.

@ThatGuyImpious
 
Sweetie Belle lives with her parents…
 
Rarity has a small business, yes, but hasn’t established any kind of name for herself until the first season, and even in the second season she’s effectively unknown despite her attempts at social climbing. Combined with her not having any paid help, even with grudge work like digging up gems, I was under the impression that she’s only started her business shortly before the start of the show and has yet to hit it big.
 
And since I reaaaaly doubt that she’s a college girl, she probably started her business right out of mandatory education.
 
And given how little she acts like her parents, I think it’s a safe bet that her persona is carefully engineered.

All that being said, I’d say he’s more 12 years old.

@Sjogre
 
Said “full time job” is him doing jobs for his adoptive sister, something he should do anyways, and housekeeping is between him and Twilight and that’s relatively normal.
 
As for cooking, remember this is Twilight’s house we’re talking about, he was only slightly more out-going than Twilight in Canterlot and probably didn’t have a lot of close friends so he had to keep himself entertained somehow.
 
Yes he is remarkable responsible for someone his age, but he’s still a child.

Spike seems like a kid who just turned 13 while the CMC are more in the 8-10 range.

@Sjogre  
Ok then, if Rarity is 20 the Spike is likely 15 and Sweetie is about 10, so like I said,m he;s not closer to one then the other or at lest not by much more the a year or so, we live in a world where we have men in there 50s or older marrying women in there 20s, a five years is nothing.

Rarity always struck me as the oldest of the six. She’s an independent business owner and is able to provide for her sister, and makes enough money that she can afford to just do things for free out of the goodness of her heart. Altruism is expensive, you know. Dash is up there too, she presents herself as a lazy youthful thug, but she’s mature and responsible enough to be the head of the weather team, and her leadership has shown on more than one occasion.

@Sjogre  
He’s not an adult and his not a kid, he’s a teen and most likely in his early to mid-teens, and the mane six are all in there early adult-hoods, the CMC are most likely close to there teen years.

@ Prof.NightJack
 
I can’t really buy Rarity being that old. Calling them more than twenty would a stretch. Rarity acts mature, but drops or fumbles that too often for it to be something other than an act.

Sweetiebelle is more Spike’s age in any case.

@ Background Pony
 
Did I imagine the part where he has a full time job? Research assistant, housekeeper, cook, and librarian might not be the most complicated of jobs, but he does all of them, which is kind of a lot of kid to do. On average, he’s not any less than the rest of them, and all of the mane six have moments of immaturity.

This is why they won’t straight out say the ages. Little kids will just find it cute.

Yeah, Spike’s only like five years younger than the Mane 6. He’s a kid, but calling him a baby is just mean.

@Sjogre  
Funny, Spike doesn’t seem much older then someone early high school at the most, so that’s at most five years in age difference, and Rarity seems like someone out of college, I would say at most the age difference of Spike and Sweetie is the same for him to Rarity.

@Background Pony  
This is what I’ve always thought, too.

Mane Six - around 20  
Spike - 14  
CMC - 8 or 10