Kanye West's feud with Jay-Z stems from the rapper "forcing Kim Kardashian West" on the Carters.
The 40-year-old musician and Jay, 47, have gone through a very public falling out over recent months and the source of their dispute is reportedly Kim, Kanye's wife.
During a concert in Inglewood, California, in 2016, Kanye ranted: "Beyonce, I was hurt. I went down seven years on behalf of your fake s**t."
He later added: "Jay-Z. Call me bro, you still ain't call me ... I know you got killers, please don't send them at my head."
At the time, it wasn't apparent why Kanye was angry at Jay and his wife Beyonce, having previously collaborated with the pair and been close friends with them, also.
But it's now reported that Kim and the Carters didn't click, which left the 'Famous' rapper feeling frustrated.
A source told the New York Post newspaper's Page Six column: "[Kanye's] rant was really about Kim and Beyonce not being BFFs. Kanye is frustrated that his wife does not have a better relationship with Beyonce.
"He wanted to put that pressure on Jay. It's like, 'We're cool and we do business together, and now our wives should be friends?'"
But according to the insider, Beyonce found there to be very little commonality between herself and Kim, 36.
The source explained: "It's not organic. It's not real. Beyonce is a Southern, God-fearing woman, despite what you may see when she's entertaining. She may not have much in common with Kim."
Despite their high-profile falling out, another insider has suggested that Jay and Kanye - who collaborated on their 'Watch the Throne' album in 2011 - will resolve their differences at some stage.
The source said: "Their relationship is familial ... I'd be very surprised if they didn't work together or have some kind of relationship in the future."