I've seen several people who think Spilight shipping is wrong or messed up, so I've decided to share my thoughts on the matter.
In my opinion Spilight is sweet, because I see Spike and Twilight as friends and that's it. Not once has Twilight ever refereed to Spike as brother or son. Seriously he is not her son for two reasons; one he is a dragon and she's a pony, two she was just a filly when she hatched him, in other words she was between the ages of 4 and 10, in human terms. Obviously the age gap doesn't seem too big, so I just don't see how that could work. And, yeah yeah yeah, I know she hatched him, but that doesn't make her his mom. Whoever laid the egg is his mom. And let me emphasize on this, SHE WAS A FILLY! That's like saying Applebloom could be a parent! THAT'S SICK!!! So obviously the "son" concept has a few holes in it.
The next idea that bugs me is how everyone thinks they're brother and sister. No, because yet again there is a species barrier.
Plus he is her assistant and best friend, nothing more nothing less. He was given to Twilight when she was a filly to be her ASSISTANT, not adopted by her. She always says "Number one assistant" not brother or son. And she says "he was my first real FRIEND" not brother.
So in my view the whole relationship between Spike and Twilight is a friendship. That's it. They are not related in anyway, via son or sibling. Not just because of the species barrier, but because they have never once refereed to either of them as being anything other than friend or assistant.
Also there is one more thing I'd like to point out. [link]
You know because you've all totally looked at your sister or mom like that before.
On another note I do NOT support Sprarity simply because I find her rather stuck up and that she doesn't really seem to care about how Spike feels. Honestly I'm a little glad that they laid back on that shipping in the show...