Story copied from source:

Ever since Twilight Sparkle first traveled to Canterlot High, she had a crush on the Flash Sentry of that world. However, she knew that a relationship with him could never work since they were from different universes. That's when she realized there was a Flash Sentry right in Equestria. So, she decided to get to know him and see where that took her.
One day when visiting the Crystal Empire, Twilight decided to strike up a conversation with (pony) Flash Sentry. After a casual yet enjoyable conversation with him, Twilight realized that this Flash Sentry was even better than his human counterpart. He was smart, funny, and generally had more in common with her than human Flash (who, she admitted, was just an immature teenager) ever could.
Twilight and Flash's friendship continued as Twilight spent more time at the Crystal Empire and they got to know each other more. After a couple years, their friendship even grew into a romance that went deeper than Twilight's crush on human Flash. Soon, their little visits turned into dates as their relationship became official.
After a few more years passed, Flash decided that he wanted to make Twilight his wife. After buttering up her brother and asking for his sister's hoof, Flash took Twilight out on a romantic night on the town and proposed to her. Of course, she said yes.
Twilight and Flash had a romantic wedding in Canterlot, free of any world-threatening dangers. Shining Armor reassigned Flash as Princess Twilight's personal guard (and husband, of course), which allowed the newlyweds to move to Ponyville together.
As the years went by, Twilight and Flash had two children together: Dusk Star and Galaxy Guard. With each child's birth, Twilight and Flash breathed a sigh of relief when they discovered they weren't alicorns.
However, the infant years weren't easy. Dusk and Galaxy had stronger unicorn/pegasus magic than the average pony, since their mother was an alicorn. Twilight and Flash, with the help and support of friends and family, were able to manage these bursts of magic. In the end, they successfully raised their children into well-rounded adults.
Twilight and Flash lived a happy life in Ponyville with their children. Looking back, Twilight was glad she was able to get over her silly little crush on (human) Flash and open her heart to (pony) Flash. Little did she know back then where a casual conversation with a royal guard would take her!