Twilight's mother, Twilight Velvet, is a social climber. Coming from money and privilege, she was raised to marry for money, and bear many a snot nosed foal and continue the cycle. Instead she fell in teenage love with Nightlight, a half moonicorn bastard. The two did as teens did, and spent many afternoons frolicking about velvet's expansive family estate. She soon found herself pregnant, and was shotgun married to Nightlight before she even began to show her pregnancy. And soon after that, Velvet and Nightlight welcomed their firstborn child, Shimmering Heart, a filly. Things went wonderfully, and they soon had a second foal, Twilight Sparkle. The family lived comfortably, Velvet stayed at home with her girls, and Nightlight worked at Celestia's school, teaching astronomy. When the girls were school aged, they auditioned for entry into Celestia's school. 

Much to the disappointment to her parents, Shimmering Heart did not get in. Twilight, however, did. Within a few short years, Shimmering Heart fell out of favor with Nightlight and Velvet, and Twilight became the star child. Shimmering Heart began to act out, staying out late, bunking school and starting fights when she went. Twilight managed to escape her ire, as Shimmering Heart knew it wasn't her sister's fault that their parents were clearly not as kind as they let on. 

When Twilight was about ten, and Shimmering Heart was 13, he came out as trans. While Nightlight was accepting, Velvet was not. Velvet insisted that her child was acting out, trying to steal attention away from Twilight out of envy. Shining Armor, having chosen his name before coming out, insisted that he wasn't doing that. Things were different in the Sparkle household after that. Velvet and Shining fought constantly, and while Nightlight was supportive of his son, he did make it clear he wished that both his wife and son would end this nonsense in some way. Twilight was utterly torn, she loved her brother, but wished that the fights would stop. 

Velvet changed, she became hyper-critical of Twilight, in some attempt to maintain control over her children. She imposed strict rules, not allowing play-dates with foals from the lottery entries to Celestia's school, taking away books with 'radical ideals', and harshly punishing poor grades. Twilight was miserable, and Shining was her comfort then, shielding her from Velvet's more hurtful words, and taking her out to play when he could. Nightlight wanted to do more for his children, but long hours at work and very little authority over his wife kept him quiet. This went on for quite a few years, until Twilight was 13 and shining was 16. 

It all came to a head when Velvet had a family photo scheduled, a luxury at a time when cameras were just becoming accessible to the public. Shining, in an act of defiance, cut his hair the morning of the photo. Nothing too short, but it was how he liked it. This sent Velvet into a spitting rage, and she screamed at Shining when he arrived at the photo studio, berating him for his 'stupid gender problems' and threatened to send him away to a girl's boarding school on the other side of Equestria if he didn't stop this right now. Shining was devastated, and allowed Velvet to style his mane into some semblance of a girls style, and posed for the photo. The argument started back up the second the photo was taken. It quickly turned into a total screaming match right in the studio, and something snapped in Nightlight. He stepped between Shining and Velvet, shielding his son from his wife's cruelty. He put his hoof down, telling Velvet that she had to either accept his son, or loose  her husband and children in a messy divorce. Velvet dug in her heels. 

There was a strange period of time in Twilight and Shining's life where they lived separate from Velvet. Nightlight and the foals stayed in their family home while Velvet stayed with her parents. Shining was able to start properly transitioning, and Twilight excelled in school. Velvet, from a distance, understood that she had fully, totally, and royally fucked up. Nightlight allowed Velvet to visit the children from time to time, mostly to see Shining. Velvet and Shining, over a number of months, came to an understanding. Twilight, being much younger, was quite willing to let Velvet back into her life. Eventually, Velvet was allowed to come home, she was able to come back into the lives of her children, and to regain the affections of her husband. It wasn't by any means easy, and was awkward and uncomfortable for almost a year, but by the time Shining was ready to finish high school, things were good again. 

Sure, Velvet and Shining aren't as close as they could be, and to this day Twilight feels like if she was better, she would have been treated better by her mother, but things are better than they were. Velvet doesn't really understand her son, but has come to see him as the man that he has always been, and loves him as a mother should. The photo taken that fateful day, which is shown above, has never been displayed in the Sparkle family home, and to this day sits unopened in the envelope it was mailed in, locked in the bottom drawer of Nightlight's desk in his study.