Sans AU Headcannons

Oreo Brothers

I wanted to incorporate the idea of Reaper, Cross, and Ink being brothers with their canon backstories, so here you go.

They all used to be human. Their parents were...not good. The mom had several affairs with other men and the dad just wasn't good. He cared for no one but himself and constantly took the anger out on the mom, neither realizing that that wasn't a good environment for children to grow up in. Reaper is the oldest, Cross is a year younger than Reaper, and Ink is a year and a half younger than Cross. It's possible that the father they knew isn't their biological father due to the mom being with so many men. Anyways, one day the father's last braincell died, and he pulled out a gun on the mom.

You can guess how that went.

Reaper, being the eldest and most protective of the trio, recognized the gunshots immediately while Cross and Ink didn't. He just told the to run, and to follow him. They found a cave after a while, and while investigating, Ink fell into the entrance to the underground, and Cross fell in as well trying to get him out. Reaper didn't want to leave them there so he jumped in too. At this point in time, the fourth human had already fallen. Toriel found them, and naturally took them in, but found out quickly that with the dangers of the ruins and for the sake of their development that she couldn't keep them, at least not like this. So she called a favor on Alphys to try and turn them into skeletons. Alphys was successful. They were brought to snowdin and were just considered skeletons that had been abandoned or lost.

They were living happily until the 7th human, Frisk, had reset. It turns out, turning a human into a monster had disastrous consequences when the code was tampered with. The potion Alphys had made not only altered their code, it basically made the code foreign to the world, and all it took was a reset to completely glitch it out of the world. Reaper was brought to Reapertale, Cross was brought to Xtale, and Ink was brought to _____tale with their memories still intact. It was decades before they reunited. 

Some other headcanons:

-If you put the sanses in a forest, the oreo brothers would have the most knowledge on how to survive, because they were just never cared much as children. They learned math and english on an old laptop, and had to learn how to do things like making a fire, purifying water, etc. They had to learn it themselves because the parents couldn't be bothered to send them to school or give them proper water and food.

-They still have some PTSD over it, so they don't have a tendency to drink and don't like hurting their friends. The treatment also caused them to have a, well, a shorter a fuse, and they can accidentally become violent towards anyone who poses a threat. It isn't as bad as othe people like Dust because they had literaly centuries more time to get over it.

-On rare occasions, when Ink drinks his vials, he gets DID, his main emotions like anger, happiness, and sadness acting as his personalities. One of them is his trauma, and depending on his mood, that personality will either be really shy, distressed, and sensitive, or angry, violent, and hurtful. 99% of the time though, he just goes into emotional overdrive for like a few minutes.

-Cross is very protective over Ink, as he feels like it's to make up for everything Ink had to witness when they were younger. 

-Reaper makes a great therapist because he's used to consoling Cross and Ink when their parents fought.