Taking to Instagram, Asghari shared his sister's big moment as she made her runway debut at the fashion gala.
"My little big sister doing her first show," Ashghari captioned the video.
Spears, who accompanied Asghari for the show, looked stunning in a skin-tight black minidress, while her dancer beau rocked a navy blue button-down shirt and white jeans.
The pair sat side-by-side in the front row at designer Michael Costello's Art Hearts show.
"You guys are such sweethearts," the fashion designer captioned a photo of the pair. "We love that you came out to support our show.