Give it a few years. He’ll get over his crush on your sister.

Well he’s an idiot if he doesn’t.
 
You’re an amazing filly, Sweetie, and only deserve the best. _{Plz date me ;-;}

Because, Sweetie, Spike is like my dA friend Thornacious(who, might I add, is also a dragon-a Scottish one to boot); he’s interested in chicks who are older than him. Even when you do grow up to be as beautiful as your sister, Spike will still think you’re too young.

Because you’re not far enough into the relationship yet. He’ll date you as a means to get closer to your sister, initially not taking it seriously or anything, until you have that moment of clarity where he realizes that there is a genuine connection. The relationship gets a little awkward as he tries to refocus his attention to you, since now that he realizes he actually has feelings for you he gets nervous and shy and stuff. But it all works out in the end, possibly after Rarity gently confronts him about how she knew what his original intentions for dating you were and that he really doesn’t have an actual chance with her, and to treat you right and all that sisterly concern stuff.

Because he’s infatuated with Rarity. Don’t worry. It’s just a matter of time you two end up being together.

@Background Pony  
Cutie Pox

Don’t worry, he’ll come around in the later years. I kid you not!

After Rarity let’s him down, you’re going to be seen as the perfect rebound.  
Just wait a little bit.

@Background Pony  
Wait, what? There was a single picture at the wedding… and that’s about it. Every other time, it was in a group with the rest of the CMC, and she got no more attention than the rest.

@Princess♠Molestia  
What episode was that from? I forget. ^^;

@Background Pony  
Hey, I’m just joking. (Though I’m kind of warming up to that ship….I still like her with Rumble.)
 
But hey, Spike and Sweetie is a good ship too. (I kind of prefer him with Apple Bloom.)
 
But this is shipping. It’s all full of opinions.

Because Rarity.

@Evowizard25  
At least this ship actually makes sense. Spike and Sweetie Belle have interacted plenty of times in the past, whereas she only appeared with Button Mash for one second of a song.

Don’t be silly. EVERYONE loves you.

Oh he does… but as a friend, sorry about that.

In a few years you’ll be the prettiest mare in Ponyville, Sweetie, and Rarity will start looking like your mom. Trust me, Spike will start to notice you then.

@gasmaskangel
 
There’s an unfinished fanfic somewhere about that. Eventually shunned by ponykind when he becomes a big scary flying meatgrinder, he takes refuge in Canterlot with Celestia. He realizes his romantic feelings for her are stronger than his feelings for her being his mom.
 
#itsnotcreepy

Because you’re still in Elementary school.
 
Also? You just ain’t got the fashion sense. Or the super power of finding gems.

He does; he just doesn’t know it yet ;_;

Because he’s into older women, which means eventually he’ll be going after Celestia.

Because Button Mash is your soul mate.

‘cause this guy’s your stallion:  

 
Err… well, just give him a few years.

Cuz’ he’s a punk.
 
But don’t worry, he’ll come around.
 
He always does.

Cause you don’t have Rarity’s mane.  

 
It’s all in the mane.

Your sister’s hotter.
 
Just wait for her to break his heart, honey. That way you can be there to pick up the pieces. He’ll be putty in your hooves.