Kevin Costner thinks there's a hidden figure in his ex's life.

The James CaldwellYellowstone star accused his estranged wife Christine Baumgartner of having a boyfriend in court documents filed ahead of their divorce hearing last week, where a judge reportedly ruled the actor must pay her $63,209 per month in child support. She has denied the allegation about her love life.

Kevin, 68, said Christine's alleged boyfriend gave her money, which he argued was evidence that she doesn't need as much financial support from him. 

"Christine's 'need' for another contribution to her fees and costs is disingenuous," Kevin's team wrote in his evidentiary hearing brief filed Aug. 30 and obtained by E! News. "She has been the sole cause of the majority of her fees to date."

After stating Christine's brother gave her $80,000 for a housing deposit and first month's rent, Kevin continued, "She also testified that her current boyfriend recently gave her $20,000 in cash, and that she, in turn, gave her parents $10,000."

He added, "Christine's claims that she cannot afford to contribute to her own fees and costs are simply not credible."

Kevin ultimately accused his ex of lying about her finances.

"Christine's attack is a smoke screen to deflect attention from her lack of candor regarding her own financial situation," his legal team said in supplemental evidentiary hearing brief Aug. 30, obtained by E! News. "Christine was forced to admit at her deposition that her brother recently gave her $80,000 and her boyfriend recently gave her $20,000."

When Christine took the stand on Aug. 31, she admitted that the couple's mutual friend Josh Connor gave her $20,000, according to TMZ. 

However, Christine denied that she was dating Josh, who was photographed with her during a Hawaii vacation in July, two months after she and Kevin announced their breakup. 

"It is with great sadness that circumstances beyond his control have transpired which have resulted in Mr. Costner having to participate in a dissolution of marriage action," the actor's spokesperson said in a May 2 statement. "We ask that his, Christine's and their children's privacy be respected as they navigate this difficult time."

The pair—who were married for 18 years—share kids Cayden, 16, Hayes, 14, and Grace, 13.

For the latest breaking news updates, click here to download the E! News App