Billy Joel and his ex wife were reunited at Billy's concert in New York City. 

Christie Brinkley had front row seats to her ex husband's sold out show at Madison Square Garden. The couple have been divorced for over 20 years.

During the show Billy serenaded Christie with his hit "Uptown Girl" The song was originally written for Christie. She even starred in the 1983 video two years before the were married.

At the end of the song a proud and smiling Christe can be seen on the big screen on stage.

Here's the orginal "Uptown Girl" video from 1983