I found a story prompt on Tumblr, I had to write it.
Twenty six year old Dipper Cipher smiled as he slouched on the couch and pulled the bill of his favorite hat over his eyes before allowing himself to think about how he ended up with such a great life.
Fourteen years ago, back when he was twelve, he had spent the summer with his twin sister Mabel in Gravity Falls. There they had found themselves constantly running into supernatural creatures, and discovered that Gravity Falls was a magnet for the odd and strange, including himself. A year later, they returned to Gravity Falls for another summer, and he'd gotten to know a certain isosceles Dorito. Sure, it was weird to date a triangle demon, but in Gravity Falls, what wasn't weird? Then, another year later when they were back in Gravity Falls, Dipper found himself in an odd situation, even more odd than usual; his male triangle boyfriend was pregnant. Neither of them knew how it had happened (though Dipper suspected that it was because he was on top for once), but they were excited at the prospect of having a kid (even though Dipper was only fifteen) and early the next Summer, Dipper found himself taking care of a baby girl with Bill.
Dipper chuckled as he remembered what he and his boyfriend had gone through when they learnt that their little girl –who they quickly named Mirage- could cast illusions at the very young age of five minutes old. And now, ten years later, they were expecting another kid.
Dipper heard someone stumbling down the stairs not even seconds before he heard crying.
His parental instincts made him quickly sit up from the couch and call for Bill as he waved his crying daughter over.
Mirage was odd looking, but that came from being half demon. There were three parts to her hair; the top, the very top, and the bottom. The top was light brown like Dipper's when he was younger, the very top was black, like Bill's when he took on his human form, and the bottom was gold, which was also like Bill's. Mirage's right eye was an normal brown color, and her left –which had a scar over it due to a zombie incident in her earlier years- glowed golden. If anyone looked close they would notice that Mirage also had small fangs.
"What's wrong?" Bill asked worriedly, appearing in his human form.
"I'm bleeding" Mirage whimpered.
"Where?" Dipper asked, scanning her for any injuries.
When he noticed that she blushed a little and tugged at the bottom of her skirt a little as if it wasn't coving her properly, Dipper could easy guess what it was. Honestly he'd been expecting it for a while now.
Mirage was smart; she knew she didn't need to verbally explain anything because her dads could read her small gestures alone.
"What's going on?" Mirage worried.
Before Dipper could reassure her that she was fine, Bill interrupted, "the elder gods demanded tribute."
Mirage blinked at her parents as Dipper made a movement to slap the back of Bill's head and Bill turned transparent, in response, Dipper stopped his hand and waited for Bill to turn solid again before slapping him anyways. Bill just chuckled.
"This is something for your aunt to explain" Dipper told Mirage, Bill took the hint and teleported them to Mabel's house.