Headcanon · 6:02pm Nov 9th, 2014
This is about the parents of the main six. This is what I believe to be true, based on what I've seen in the show.
Rainbow Dash:
Rainbow Dash once had a mother and a father. Her mother loved her very much and was a sweet mare. Her father was a fun-loving man, who was like a best friend to Dash. Her mother got sick when she was three and passed away. She doesn't remember her, but has been told countless stories about her. She was raised by her father, and that is why she's a tomboy. Her father took her to sporting events (as shown in the picture above) and encouraged her to work on her flight. She was sent to flight camp to harness her skills and to help her become more precise and less reckless with her flight.
Fluttershy:
Fluttershy has a mother and a father. Her father is an earth pony. He is similar to Big Mac in many ways, as he is similar in build and his peaceful outlook, but he said much more. He is a nice stallion. Her mother is a pegasus. She is graceful, passionate and loving. When she fell in love with her husband, she moved out of Cloudsdale, and they lived on the ground, together. They had a baby, Fluttershy, and they took care of her for the first five years of her life. But, because they stayed on the ground, they noticed that Fluttershy had weak wings and was not trained in flight. So, they sent her to live with her aunt—she was her mother's sister and they were incredibly close as both sisters and friends, so she was perfect to take care of Fluttershy—and she went to flight school to become better at flying. She lived with her aunt until she was around 10 before she discovered the ground. She loved it and didn't remember it, since she was young at the time, other than just the few memories of her in her home. She got her cutie mark, but continued to live in Cloudsdale until she finished flight camp. She would go there everyday after school and help the animals. When she finished school, she moved back in with her parents—she was 11 at the time—and she lived with them as her parents for the next 7 years before she moved out.
Applejack:
Applejack had two parents. Her mother was a kind mother, known for her baking and pony skills. Her father was a farmer and stuck to what he knew, bucking and farming. He was a stern, but wonderful father. One day, when he was out bucking, he had a heart attack, so they rushed him to the hospital. He ended up dying in the hospital. A few months short of a year later, her mother went for a routine physical/check-up. It was there that she learned she was pregnant. She had been pregnant when the father died. She carried the baby, Applebloom, to term and the baby was healthy, but she died in childbirth. Now, with the loss of both her parents, Applejack was having trouble staying calm, and had to leave to go to Manehattan. In the above image, you may notice that Applebloom was not there. That is because AJ had said goodbye to her, earlier, and they put the baby to bed when she left so that she wouldn't be sad when she actually left, in the hopes that she wouldn't even be fazed by it. But, AJ did come back when she realized that she had to be there for her family, and especially her baby sister, after the losses. They were then raised by Granny Smith.
Pinkie Pie:
Pinkie Pie's mother got pregnant when she was only 16 (I'm referring to human years because I don't know how else to put it. Human and horse years may even be the same. I don't know.) She was a crazy, party mare who craved excitement. She gave birth to, and loved Pinkie Pie to pieces, but knew that she could take care of her. She stayed with her for the first couple years of her life, her parents helping all the while, but knew that they both deserved better. So, she sent Pinkie Pie to live with her older sister, who had recently had children of her own, because she felt it would be a more stable environment. Pinkie grew up among her "sisters" and lived with her parents, but her mother's energy remained inside of her and she wanted to have fun. One day, she finally threw a party, and that party reminded everyone of her mother, and her new mom (the one raising her in the picture) remembered the fun she used to have with her little sister. From then on, the reigns loosened and life became better. When she became an adult, she visited her mom after having never really met her, and they both surprised each other with a party, at different locations, of course. She forgave her without a second thought, and they always hang out at the yearly reunions. Pinkie's "parents" send letters to her, often, and she always writes back.
Rarity:
Rarity's mother and father were high-class ponies, living in Manehattan. They met each other, and got married as they were both of equal class. Her father was a stuck-up, egotistical jerk who found babies to be gross. Her mother was also fancy, but she was a wonderful, caring mare who hated the father's personality. She loved Rarity with a passion and when Rarity was around three, she and the husband divorced as she didn't want him to negatively affect their daughter. He left, easily, and fell out of contact with both of them, wanting nothing to do with either of them from then on. She raised Rarity, alone, for several years, but when she was nine, she met a stallion from Ponyville. He is the stallion in the picture above. He is goofy, stupid and lovable. She wanted that type of person. So, they were married and fell deeply in love. They then moved to Ponyville, where he was from. The two of them then had a baby, Sweetie Belle. (Her mother was white with a purple mane, and he has a slightly darker variation of white, so that's why Sweetie still looks like Rarity.) Rarity was happy to have a father, even if he was uncouth, a word which she had remembered her biological father using, even though she was just a foal. They remained happy, until Sweetie Belle was 5 and Rarity was 14. Her mother was hit by chariot, and died immediately. Rarity's biological parents were gone (still her father was out of the picture and did not attend the funeral), but Sweetie still had her dad. They were then taken care of by the father until Rarity was seventeen and Sweetie was eight. Then, the father went into Sugarcube Corner, a newly opened bakery in town. There, he met Cup Cake. They got to talking, and she set him up with her sister. (Look at the mare in the picture up there. Now, look at Cup Cake: 
They are incredibly similar in color scheme and in body build. That is why I believe that they are sisters.) She was a fun, kind of stupid, but very happy mare. She was easy to talk to and he really liked her. They soon married, four years after his wife had died. Sweetie lived with the two of them, but it was awkward having a new mom, and she spent a lot of time with Rarity. Soon, she almost officially moved in to Rarity's house, sleeping over often and practically living there. They understood, as it was a big change. That is the current situation. Rarity and Sweetie both like their mother, but the circumstances are odd. P.S. That is why Rarity is so high-end and Sweetie is more down-to-earth. They were raised by different ponies.
Twilight Sparkle:
Twilight lived with her parents for the first ten years of her life. Her parents are great, average parents. They had important jobs, and held close ties with the princess, as they both worked with/for her. Because of this, they were often away from Twilight, but only for the standard work hours, and so during that time they needed a babysitter. Due to their good relationship with Celestia, she had her niece, Cadence, babysit Twilight. They also worked in a lot of brother-sister time between her and Shining, so that is how Cadence and Shining grew fond of each other. Soon, she got accepted into Celestia's School for Gifted Unicorns, and also became the personal student of Celestia. Once that began, Celestia took her under her wing during the time she would have been babysat. Cadence no longer had to babysit Twilight, but Spike now needed someone to love him, so she took care of him. (This close tie with him made her feel very close to him, and that is why she had no problem being thrown off of a tall castle to save him. He was kind of like her baby.) And, Twilight only stayed with Celestia during school hours, and would always spend the mornings, nights, and weekends with her parents and brother. Spike and Cadence would often visit, however, and when Spike was old enough, he would sit in on lessons with Twilight and Celestia. This is how he came to enjoy Twilight's company and why he moved in with her. Twilight now writes her parents, often, and Celestia, too, as you know. Shining Armor and Cadence still remain a big part of her life, especially now that they're newlyweds.
Um, a problem with Pinkie. We've met her mom. Cloudy Quartz. In "The Cutie Mark Chronicles." She's rather reserved and conservative, at least now. We've also met her presumed father, Igenous Rock. Lean, wiry, patriarchal farmer sort.
2584209 There's no issue with that. She had a mom and she gave her to the couple you're referring to. On the show, she had already been given to Cloudy Quartz. I'm just saying that her biological mom is not that mare, but that she has taken care of her since she was a foal. I'm taking that episode into account.
2584322
Okay, that works. In the Shadow Wars, Igneous is not her biological father, but rather the Paradise Entity (a godlike sapient AI from a previous cycle of Pony civilization). She calls Igneous her father and the Paradise Entity her sire; she loves Igneous as if he were her biological father.
2584334 Interesting.