NHL Star Johnny Gaudreau Killed Hours Before Sister's Wedding

7:17 AM PT -- A church official tells TMZ Sports ... Katie Gaudreau and Devin Joyce's wedding has been canceled in wake of the tragedy.

NHL superstar Johnny Gaudreau and his little brother, Matthew, died just hours before their sister was set to get married.

Katie Gaudreau and Devin Joyce were scheduled to the tie the knot at a ceremony at 1:45 PM on Friday at a church in New Jersey. According to Katie's Instagram page, the couple had actually rehearsed the event on Thursday night -- just before the Gaudreau brothers were tragically killed.

Katie and Devin's registry showed Johnny and Matthew were both slated to be groomsmen. Johnny's children were listed as the wedding's flower girl and ring bearer. Johnny's wife and other sister, meanwhile, were named one of the maids of honor.

It's not clear yet if the nuptials have been postponed ... we've reached out to church officials for comment, but haven't heard back.

As we previously reported, Johnny -- the Columbus Blue Jackets' best player -- and Matthew were riding bicycles at 8:19 PM in Oldmans Township when an alleged drunk driver struck them from behind.

Cops say the two sustained serious injuries and died at the scene. Police added the driver, Sean Higgins, was arrested on two counts of death by auto for his role in the crash.

Johnny was 31 years old. Matthew was just 29.

RIP