Mariah Carey's close relationship with her ex-husband, Nick Cannon, is reportedly causing tension between the pop diva and her boyfriend of six years, backup dancer Bryan Tanaka.

Insiders have told The National ENQUIRER that Tanaka, 39, has held off on proposing or having children with Carey, 54, due to concerns about her ongoing connection with Cannon, 42, who is the father of her 11-year-old twins.

"Bryan is tired of feeling like second best to Nick," a source discloses. "It's been the elephant in the room for years now and the main reason he hasn't proposed or had kids with Mariah himself."

Though some may perceive Carey as controlling her younger partner, insiders assert that Tanaka is his own person and is becoming increasingly bothered by the "creepy vibe" between Carey and Cannon. "Mariah and Nick are on the phone constantly, and they get affectionate whenever he comes to town to see the kids," the source reveals.

According to the insider, Carey prefers to keep Tanaka at a distance when Cannon is around, further exacerbating Tanaka's suspicions.

Last year, Carey reportedly considered seeking full custody of her twins with Cannon, Monroe and Moroccan, despite the joint custody agreement that has been in place since their 2014 divorce. However, sources say she has since changed her mind.

"Bryan wanted her to go for full custody so he could get some space from Nick," the insider shares. "But she hasn't pulled the trigger and Bryan's understandably upset."

Despite Tanaka's frustrations, it seems that Carey remains largely unfazed. "He's fuming about it, but Mariah doesn't seem to care!" the source concludes.