Birthday Bios: Peanut Butter · 3:27pm Jan 21st, 2016
How do ponies even play basketball? I've seen a couple of basketball cutie marks, so it has to exist in Equestria... 
Anyway, let's get on with our precious Peanut here...
Born in Manehattan to chemist team Acorn Compound and Cocoa Butter, Peanut Butter Sandwich had come out as a rough-and-tumble colt. The moment he stood up, he'd be galloping around the house, chasing his mock-frightened parents. He often climbed into places that he shouldn't be, and Acorn and Cocoa had to keep the door to their lab locked, considering the chemicals that were not safe for anypony to ingest, especially a little foal. Thankfully, Peanut preferred to climb into the cabinet to stuff himself with peanut butter.
Peanut loved visiting his grandparents. Grandma Panini enjoyed doting on her first grandfoal, giving him cookies and letting him play with some old toys. Peanut also enjoyed banging on Grampa Beans' piano, throwing around the music sheets, and jumping off the bench in attempts to fly. And then there were the times where he tested Uncle Hay Burger's patience, making a mess of books, files, papers, and other things that poor Hay had spent hours organizing. Didn't help that Peanut's mother, who was Hay's sister, thought it was kind of funny.
Acorn's parents enjoyed having Peanut over as well, seeing as he was their only grandchild, coming from their only child. He enjoyed all the attention received by all the grown-ups in the family, and for five years, he had felt like the center of the universe.
He found himself no longer the sole grandfoal of Beans and Panini when Uncle Hay and his wife Mozzarella had a baby, a colt they named Cheese Sandwich. He was okay with having a cousin, although Cheese was a strange baby that managed to pop into odd places somehow. Still, a part of him was annoyed that whenever both cousins happened to go to their shared grandparents on the same day, the grandparents seemed to give Cheese more attention. At least he didn't have any cousins on the other side of the family, and Grandma and Grandpa Nut were all his.
And then Peanut got a sister.
Peanut was very jealous of the new baby, Ice Cream Sandwich, born just a couple days before the new year. All of the attention that was once all his had now been divided 24/7, and as his sister got older, he developed a habit of picking on her. His teasing streak also bled over into his relationship with Cheese, who was developing a timid streak and reacted by hiding. It wasn't until Peanut started to pick on Cheese's brother, Tomato Sandwich, that Cheese started to fight back. Cocoa Butter had noticed Peanut tormenting his younger relatives, and often cracked down on him, dragging him by the ear to his room whenever he made one of them cry.
When he wasn't teasing his sister or doing homework. Peanut spent his time with a group of friends that liked to play basketball. It was a strange sport of having to bump a ball into a bottomless basket hung from a wall, but he found that he enjoyed it. His style of play aiternating between the regular bumping of the ball, and dribbling it with his tail. His friends thought the latter was weird, and for a while, it provided a window of easy stealing. It took Peanut a while to refine his tail movements to get rid of that weakness.
He also liked to watch his parents perform some experiments, whether it was trying to create the perfect cleaning mixture or a formula for making Cocoa's potted plants grow better. Peanut once sneaked into the lab to try to create something; his father had caught him just as he had mixed ammonia and bleach. The house was quickly evacuated after that, and he was grounded.
Peanut was eight when Grandma Panini was killed in a carriage accident, and Grampa Beans' heart gave out just a few weeks later. He's the only one of their grandfoals who remembers both funerals clearly. He often played street ball in order to cope with the loss, unsure if he would be able to handle seeing his mother in so much grief.
Peanut Butter and Ice Cream had been steadily visiting their cousins less and less, and Peanut was an adult by the time he figured out the reasons why: Uncle Hay was still bitter about being picked on for years by Cocoa, he was having marriage troubles with Mozzarella, and neither he nor Ella didn't quite like Cocoa voicing her concerns with how their family was headed toward dysfunction. The visits came with more arguing from the adults each time, the kids isolated from the fights in another room.
One such fight spurred Peanut and Ice Cream's parents to accept a job offer for teaching chemistry, and then moving across the country to Seaddle when Peanut was twelve. Peanut was pretty angry at them for the action, and it took him about a year to cool down and make new friends. He still played ball, whether alone or with friends, and going one-on-one with a bully that insulted his pride had him earning his cutie mark.
Happy to get a sporty cutie mark, as befitting his interests, Peanut went ahead and pursued a career in basketball. As a teen, however, he found a lot of his peers found his decision funny and picked on him for it due to one reason: he was short. His growth spurt wasn't that much of a growth spurt, and everypony found it funny to imagine him doing great leaps for a slam dunk. A couple of jerks even mentioned that "Peanut" was the perfect name for him. Feeling rather prickly about it, Peanut got into a lot of fights.
Still, he got the last laugh when he invented a method for a good slam dunk: he used his tail as a springboard.
As he grew older, he was less and less interested in picking on his sister. With Ice Cream being so cool-headed, quiet, and pretty, he found that she was attracting a lot of boys. She was also being bullied by other girls for being the strange nerd that had far more cow friends than pony friends. His jealousy a thing of the past, he was quick to shoo away those that bugged Ice Cream. He was especially keen at detecting scumbags. All the while, he tried to mend bonds with her by going out for ice cream with her, getting to know some of her cow friends, and playing in the park. His friendship with his sister made him realize just how stupid he was in tormenting her, and he decided that one day, he'd go back to Manehattan to mend fences with his cousins.
When a young adult moving out and into his first house, he was caught by a surprise housewarming party, thrown by his then-teenage cousin, Cheese. Having not seen each other in years, Peanut's first thought was, "What the heck are you doing here?" in a very confused manner. His second was annoyance at how much taller Cheese ended up than him. Still, he was happy to see his cousin again, eager to take the chance to form an actual friendship with him. It somehow turned into Cheese poking fun at his height. Peanut was still annoyed, especially since that was clearly revenge for the torment of the past. Still, at the end of the party, they parted on good terms.
He was confused to learn that Cheese was estranged from his family, and his heart sank upon learning about the especially strained relationship with his brother. Peanut tried to press for the reasons why, but he quickly learned that angering a party pony was not a smart idea. So he was left to wonder what the heck happened, and considered going to visit Tomato to see if he could find out from him. He hasn't done so yet.
Still in pursuit of his career, he soon got his big break in Equestria's Basketball Association draft, and was selected by Applewood. He moved there in order to play for that city. His quirky style of playing attracted many an adoring fan, and he ultimately met a mare named Jelly Jubilee and befriended her. Friendship turned to love, and soon enough, they got engaged.
Spoiler for Brotherly Bonding Time: Cheese and Tomato are going to attend the wedding.
It's nice to see that not every part of the Sandwich family tree is a thick wedge of angst between two slices of dysfunction, and that the cousins manage to mend their bridges.
3702328 It seems to be entirely dependent on how close they are to Hay and Mozzerella, they are the swirling center of horribleness that everyone else needs to escape.