If you have to have an ex-husband, you could do WAY worse than Billy Joel.

The singer isn't just friends with former model Christie Brinkley, he seems to absolutely adore her. At his recent New York City gig, he was more than happy to reminisce about their good ole days by serenading her with the hit song "Uptown Girl," which he wrote for her in 1983. Sitting in the front row, Christie beamed proudly before posting a few pics from the night on her Instagram.

The unlikely couple was married in 1985 and divorced in 1994. They had one child, Alexa Ray, and Christie went on to quickly marry another man -- like the same year they split. But here's what's great about these two: you never heard Billy say an unkind word about his gorgeous ex, and Christie doesn't think twice about singing Billy's praises on her Instagram. For example, in this pretty pic taken with her daughter Sailor, Christie wrote: "He's still got it! #msg #franchise #nationaltreasure:

Awww ... and here's another sweet one of Sailor snapping a photo of the Piano Man playing the piano:

I love how these two have put family first and how even the children Christie had after being married to Billy show him plenty of respect and fan love. I'm guessing the key to their successful union is mutual respect AND a respect for privacy. These two are living by the words: if you don't have anything nice to say, don't say anything at all.

And, by the way, both Billy and Christie appear to be single right now -- or at least not married -- so is there any chance they could reunite and be adorable together? Any chance at all?

Ah, well. At least there's this vid of Billy singing "Uptown Girl" to Christie and cutely gesturing for the camera man to turn his lens on her:

Could you picture yourself being good friends with your ex?