First and foremost, as I have not even looked at the chapter yet, I can say that your description is incredibly off-putting. You, the author, are talking to us directly about the story. What you should be doing is describing the premise without any references to yourself or the "real world". For instance, looking at your description, I could write :

"Twlight Sparkle is one of the most powerful unicorns in existence. At the young age of 6 (or whatever, your fic), during her exam to enter Celestia's School for Gifted Unicorns, she experienced a powerful magical boost and lost control over her massive, untapped magic reserves. Among a sea of chaotic magic, hatching a dragon and turning those present into potted plants, an abnormality occurred.

Twilight created new life.

The young stallion, physically the age of Twilight, was adopted by Celesita, who had come to quell the disturbance. Dusk Shine, as he was named, grew strong under her tutelage. But soon, it will be time for him to leave the nest and grow on his own.

Next. Anytime a description mentions a "1st fic", it is often not looked at or not taken very seriously. Avoid mentioning things about yourself unless it has something to do with the story. When noting an image used that isn't yours, simply put "Cover Art by: (insert link to artist's page here)"

That's what I got. Hopefully it helps

having twilight and dusk in the same fic while the rest of the mane 6 go after him. i am intrigued.

3430773
So is Twilight not considered his sister.

3430960 no she is not because she created him if any thing consider her his mother or simply the pony that is a reason he exists.

3430773 I thank you for your advise but the fact is that i don't know the creator of the image other wise i would have put his or her name with it and i put the "this is my first story" for a reason that being said thank you for your thoughts.

3430845 stick around and it might get even better

I downvoted this story not because it sucked so much ass that it needed to be downvoted, even though that is true, I didn't even downvote it because you were being a prick in the comments, even though that doesn't help, I downvoted it because you actually use bing.
For shame.

3432895 hey i use Google to but Bing is my preferred web search and i know i was being a dick and i have apologized for it

3431002 like i said i don't care if he was I'm thank full that he told me but 7 other people did as well i needed a editor to fix my grammar not a teacher to tell me what i did wrong then not give me any real help if i wanted that i could ask my drunk of a father for it thank you for your comment but leave me to fail or succeed on my own if i crash and burn its my fault not yours or any one else.

3431955 look no one said you had to read it thanks for the comment but if you have to say something about how much of a ass i am be thank full you haven't met me in the real world okay because id ruin your out look on a lot of things or make you die laughing one of the two.

3437423 it is my first language but I don't have a eye for details so I often miss my grammar mistakes and thank you for the read.

I wouldn't mind proofreading for you. I like the way the story is going. I also like @Thethhron's synopsis

3438226 well ok then I would be happy to have you as a proofreader send me a mail massage and I'll send you the next chapter to look at after I finish wrighting it

3438551 don't use bad puns for one and I reserve the right to delete them if I want it is my story and don't give me stuff about civil rights and all that because you have no rights that's a fact there man made so I have the right to say and do what I want as you do to just I have the right to get rid of your comments

3438586 Or you have the right to be angry because people tell you to improve your writing skills. I suppose never getting better is better than nothing at all. Tongue Twister.

3438618 no you don't understand me if I could edit it my self then I would but as I explained I don't have a eye for detail so I need a editor to help because when I go through and read it to fix it my self I know how is supposed to sound so I don't notice any of the grammar mistakes.

So... Many... Run-on sentences...

Suggestions! Because I’m annoying like that.

I’m not a grammar nut, and I have a personal proofreader/editor/pet grammar nazi that I have go over my stuff because of it. Still, I grimaced at points; because of the run-ons. You need to reformat the story and use periods in place of some of your commas. You tend to ramble on, and on, and on in your sentences. This makes it hard and frustrating to read. Periods are a natural stopping point, giving the reader a chance to absorb the contents of the sentence. A lot of your sentences, nay some of the paragraph look-a-likes need to be broken up and separated.

I won’t poke at the plotline too much because I haven’t seen where you’re going with it yet. Though I do like the concept.

Story writing! Some parts you could use more detail; namely in the background and in the characters. The story is just beginning so you reasonably don’t have much in place yet. It just feels like a lot of Dusk Shine's lines were taken directly from Twilight, pushing her almost entirely to the side in some cases. This wouldn’t be so bad since you’re managing a literal genetic clone raised alongside its originator, but it shows more because of the nature of the story. The way you’re working with him as a character almost makes this seem more like a Rule 64 instead of a… twin/clone situation?

Show, don’t tell. This is incredibly frustrating for many authors, but necessary to get your point across. For example; telling a person ‘They saw a pegasus’ won’t push across the fact you’re imagining the character seeing Rainbow Dash or Fluttershy for the first time.

Mostly, find yourself a proofreader and have them help you rewrite the first chapter and so on.