Since reuniting with Sunburst, Starlight Glimmer visited him more often and they caught up on each other’s embarrassing pasts. They did get busy with their own lives from time to time, as many friends do. Starlight continued to learn lessons of friendship under Twilight Sparkle’s teachings, and Sunburst was a mentor to Princess Flurry Heart. Even when life was busy, they always made a point to see each other.  
Starlight began to grow bored of living in Twilight’s castle. Twilight could tell Starlight was in need of some adventure, so she encouraged her to go out on her own and make some friends, much like somepony had once told her. Starlight did just that. She wandered around Equestria for a few years, making friends and learning valuable lessons. She also spent some time with the ponies from the Equality Village and continued to make amends for her past mistakes. She reported her findings to Twilight whenever she learned something new. Starlight was definitely learning more now that she wasn’t restricted to Ponyville.  
Eventually, Starlight felt she was ready to settle down and find a place to stay. That’s when she remembered her oldest friend, Sunburst. She went to the Crystal Empire, bought a house, and reunited with him again.  
As they were able to spend more time together, they began to develop feelings for each other. Soon, they even began to date.  
One night, during the first Crystal Fair hosted by the now-teenaged Flurry Heart, Sunburst and Starlight got engaged. They had a relatively simple wedding in the presence of their closest friends, and, of course, the princesses. The two lived happily as a married couple in the Crystal Empire from then on.  
After a couple years of marriage, Starlight gave birth to their sun, Shining Star. Since he was born in the Crystal Empire, a crystalling ceremony was held for him. His crystaller was Flurry Heart, who did it as a way of saying thanks to Sunburst for being her mentor.  
Starlight, Sunburst, and Shining Star have lived a comfortable and happy life in the Crystal Empire ever since. Flurry Heart became Star’s mentor, and he’s had an upbringing of love and unity as well as knowledge and education. The family does visit Ponyville from time to time, but the Crystal Empire has become their home.