The trio caused a stir when surveillance footage appeared to show Solange kicking and punching her brother-in-law as they left a party at the Standard Hotel following the annual fashion bash last May (14).
The Drunk In Love hitmaker later issued a statement declaring her husband and younger sister had "worked through" their disagreement, while Solange insisted she was "at peace" with the incident.
Solange was among the first stars to arrive for the 2015 event at the Metropolitan Museum of Art in New York City, walking the red carpet hand-in-hand with her husband Alan Ferguson.
The singer turned heads in a printed Giles mini-dress with pleats made to look like an open fan, a nod to the event's theme, China: Through the Looking Glass.
Other celebrity couples at the event included George Clooney and Amal Alamuddin, Kim Kardashian and Kanye West, Sofia Vergara and Joe Manganiello, John Legend and Chrissy Teigen, Amanda Seyfried and Justin Long, and Diane Kruger and Joshua Jackson.
Guests at the Costume Institute Gala Benefit also included Sarah Jessica Parker, Jennifer Lawrence, Kerry Washington, Anne Hathaway, Bradley Cooper, Uma Thurman, Jessica Chastain, Julianne Moore, Cher, Madonna, Selena Gomez and her ex-boyfriend Justin Bieber.