Let's go back to the 2000s. Around the turn of the millennium, Kanye was a young producer, while Jay-Z was one of the most popular rappers in the world. In 2000, Ye began producing music for artists on Roc-A-Fella Records, the label co-founded by Jay-Z, and he had a big impact on the success of his 2001 album "The Blueprint" (via BBC). Despite growing in popularity as a producer, West wanted to be a rapper himself and released his critically-acclaimed debut album "The College Dropout" on Roc-A-Fella in 2004 (via NME).
On his third album, "Graduation," released in 2007, West included the track "Big Brother," about his relationship with Jay-Z. While the song was complimentary at first, with West talking about his mentor and collaborator in a positive light, he then went on to talk about their "sibling rivalry" and commented on Jay-Z imitating him by putting out a song with Coldplay. However, it was taken well by Jay-Z, who described it as a "fair portrayal from a little brother's perspective" (via High Snobiety).
Of course, we can't forget about that incident at the 2009 MTV Music Video Awards either, when West crashed the stage and interrupted Taylor Swift's victory speech, arguing that his friend — and wife of Jay-Z — Beyoncé should have won the award instead, during and after which the singer was visibly embarrassed (via Billboard).
