Needs more spacing, and there's a lot of grammatical errors, I can see this being a decent fic. You've just gotta make it that.

1515049 Thank you for understanding.

1516808 no problem, truthfully, i really enjoyed this

1516996 ^^

Motherbucking wall of text. Please add spacing

Arrgh! This be poorly written and solely for the sake of clop. There be no story and no interest other than to those who like tales of rough acts between two sisters.

Neigh, tis not something that most would find appealing.

1512525 Damn right.

gifattack.com/wp-content/uploads/2009/06/pool-dive-fail.gif

Focused review time.

General structure: While the re-edit improves on the block of text formatting of the first chapter, it still could use some work in separating out each paragraph. Indenting the lead sentence helps to break up each paragraph but putting in a full empty line between each paragraph would make it easier again.

One thing to always keep in mind is that a new speaker must always be placed on a new line.

keeping a good jogging pace, she noticed the weather started to get a lot worse,

Always start a sentence with a capital.
the second half to the sentence feels like it is missing a word or two.
E.G. she noticed the weather had started to get a lot worse.

Additionally the entire paragraph runs on for a long time without a pause.

keeping a good jogging pace, she noticed the weather started to get a lot worse, she soon sprinted to the house, clenching the handles and pulling with all her might against the jammed door, it soon swung open, having her soon slam against the edge of the house

Full stops should be used after 'a lot worse' and 'the jammed door', breaking up the paragraph into digestable chunks.

"You bitch, you only like me as your incest doll!" She said with a little louder tone, Marduk heard the argument, he stepped into the living room, standing over Darklight and looking down at her. "How long have I told you, your sister would never do that! Now say sorry."

Again, this has overuse of commas instead of full stops. This line also implies that this would not be the first time that Darklight and Canni have had sex, yet Dark seems not to know how sex feels later on.

He walked into his room, starting to pack his stuff of for his trip to Trottingham, even though he was the only human in Equestria.

Two questions from this line, If Marduk is human then what does that make his daughters? adoptive ponies? And why would being a human mean that he does not have to pack anything?

Darklight scrunched up her face, having the sticky liquids of sperm leak out of her small slit, then letting out a landslide of more.

When did sperm become part of this story? woudn't that require a male participant? Maybe change sperm to 'climax' or 'orgasm'.

Finally a selection of spelling and grammar mistakes that would benefit from an additional round of proofing.
hoove (multiple instances) should be hoof
Darklight's face was completely read (red)

Understand this is not a nag post, the story has the potential to be a decent clop. It just needs some more TLC first.