What's the greatest wedding gift of all for for a diehard Backstreet Boys fan? Have one of the guys crash your wedding. Yes, it happened.

Howie Dorough, one of the five members of the band, decided to make that dream come true for Ryan and A'riel Kastovich. He not only wished them well, but sang their favorite song to them, 'All I Have to Give.'

Here's the video invitation created by the Ryan and A'riel.