Gold-medal winning Canadian curlers Kaitlyn Lawes and John Morris tasted Olympic defeat for the first time on Thursday when they were upset by a pair of betrothed Norwegians.

Kristin Skaslien and Magnus Nedregotten, engaged to be married, downed the top-ranked Canadians 9-6 on day one of the mixed doubles tournament here.

While mixed doubles is only making its debut in the Pyeongchang Olympics, Lawes and Morris each have a gold medal from the traditional single-sex version of the game. Morris won his in Vancouver in 2010, and Lawes got hers in Sochi in 2014.

The two were each 11-0 in Olympic curling play before Thursday's loss.

Mixed doubles curling is one of four new events in the 2018 Winter Olympics and was the first event overall to kick off official competition. The Pyeongchang Olympics formally opens on Friday and runs through Feb. 25.

Siblinghood triumphed over matrimony as American pair Becca and Matt Hamilton beating Anastasia Bryzgalova and Alexander Krushelnitskiy in the mixed doubles curling.

The Americans started strongly and never looked back in a 9-3 win over married Russian couple Bryzgalova and Krushelnitskiy in the first of seven rounds of preliminary play.

The Americans built a 3-0 lead in the first end when Becca Hamilton knocked two of the Russians' stones out of scoring position.

The Americans never trailed after that first end and the game was called after seven ends when they had amassed an insurmountable lead.

The Russian duo, who became visibly agitated with each other following some missed shots, did not speak to media after the match.

The Americans' performance was not without its own awkward moments, however, as Matt Hamilton lost his balance as he was sweeping in front of a stone late in the match and fell heavily on to the ice.

He popped straight back up and finished the game with no visible difficulty.