Sami Zayn and Kevin Owens go way back, with both having come through the indie scene back in Canada. Zayn and Owens have been best friends for a long time, and have portrayed that on WWE television as well.
But Owens hasn't necessarily been a good friend to Zayn. The former Universal Champion has turned on Zayn more than once.
The first betrayal happened in NXT at NXT TakeOver: R Evolution in 2014, after Owens' debut match against CJ Parker. After Zayn won the NXT Championship in a match against Neville, Owens came down to congratulate his old friend before powerbombing him into the ring apron. The two had their match for the NXT Championship at NXT TakeOver: Rival, where Owens won the title.
Owens and Zayn while wrestling in ROH as Kevin Steen and El Generico, respectively, wrestled The Young Bucks at Final Battle 2009, where after losing the match, Steen (Owens) turned on El Generico (Zayn) with a lowblow. The two had a great singles rivalry following that show.