Hello everybody this is my first time writing like this and I hope you enjoy this and check out my other story's so let's go
Note you are 13 yang is 12 and ruby is 11 at this point in time

YourPOV
"Why can't they just love me like a son and I don't know why they just started this on my fourth birthday that's when yang was born then after her is ruby but ruby helps me."
No onesPOV
So you all must be wondering what happened between those years well let me show you
*Flashback* YourPOV 4 years old
"So as I was waiting for mom and dad to come home I heard a knock on the door."
Y/n:coming
(You then open the door and see your parents with yang)
Tai:go back to your room you prick
Raven:but before you go
(She then slashed you chest lightly)
Y/n:y-y-yes s-s-sir(you say because of the pain)
Raven:now honey I have to go
Timeskip 1 year still YourPOV
"I still can't have freedom and when summer came along I thought that I was saved but that was hope and the first time she saw me she shot me with her sniper in the leg now I'm waiting for a new sister."
(Knocking)
Y/n:(I then open the door to see my bitch and dick of a dad with my baby sister) Sir what do I do now
Tai:go back to your room
Summer:(She then used her scythe part and slashed my back)
(Then ruby started crying because they hurt me)
Tai:look what you did
(Summer then placed the baby ruby down)
Summer:(She then started to aim at me but)
Ruby:don't hrt big bruther
(I was on a knee because I didn't treat my cut yet and she then tried to walk to me but fell on her but and she eventually made it and hugged me)
Y/n:heh hello ruby(note now you will act like sans with ruby)
Ruby:brng me to room
Y/n:alright (you say trying to not grunt from the pain)
Nighttime
ThirdPOV
As you fell asleep with ruby on top of your chest you then appear in a dark place
???:hello
Y/n:who are you
???:I'm Gaster and I'm here to help you and my self

Y/n:uh what do you mean
Gaster:I'm slowly being killed so I would like to give my powers to you
Y/n:but won't that kill you
Gaster:yes but it will be painless
Y/n: "if I get this power I can protect ruby and help him die without suffering."alright I accept
Gaster:well then my powers are yours but you will awaken them when you turn 13 and I'm sorry for that with your family
Y/n:no problem as long as I can protect ruby so why are you turning into dust
Gaster:well I transferred my powers as soon as you said yes now with out them I will turn to dust so good bye and use them wisely
YourPOV
"I then wake up with ruby still on my chest but with her clinging onto it so I wrap my arms around her and she calms down."
ThirdPOV
And now as time went on they start to beat you to near death but ruby she always patched you up but then they started using there weapons on you then yang and summer stared shooting you and raven cane back two years later but she would use you as a practice dummy everyday and then this went on for about six days a week but raven didn't let you rest once on the seventh day she saw that as her own day with slashing at you then on your thirteenth birthday raven,summer,tai,and yang then blasted off your arm but thanks to Gasters powers now yours the arm regenerated back after one day and ruby always slept in your bed with you never with the others now back to the present
Flashback ends
Y/n:ruby I'm going to leave tonight but this necklace will tell you when I'm near also when the eyes of the Gaster blaster head light up with a red glow and then turns into a x like glow I'm in a 5 meter radius ok
Ruby:yes big brother (she then puts on the necklace)
Nighttime YourPOV
"Heh stupid people leaving a window in my room now then let's go."
(You then jump out the window)
Y/n:ah finally free

And that's the end now I hope you like the beginning of this and what not so as always I'll see you in the next chapter ah byyyyeeee