Kylie Jenner will reportedly help rapper boyfriend Tyga win full custody of his son, King Cairo, once she's a legal adult. The 17-year-old is vowing to stick by Tyga’s side during the upcoming custody battle with his ex-girlfriend Blac Chyna.

A source told Hollywood Life on Wednesday that once Kylie turns 18, she will go to court and testify on his behalf and tell the judge “what an incredible father he is.” Kylie will become a legal adult on Aug. 10.

“She’s told Tyga to cherish each and every second with King,” the source added. “To love him even harder than he ever has before and continue being a good father.”

TMZ on Tuesday reported that model Blac Chyna, 27, was seeking sole custody of the former couple’s son but would allow Tyga, 26, weekend visitation rights. Blac Chyna reportedly felt that Tyga’s involvement with a minor shows “bad judgment that translates into his parenting skills.” She also felt that Kylie was immature and said she didn’t want that type of influence around her son.

A source close to Tyga told TMZ on Wednesday that he didn’t feel that the rapper’s relationship with teenage Kylie had anything to do with his parenting skills, and that no one should question his ability to be a good father. The source also said that Blac Chyna is simply jealous that Tyga chose the youngest member of the Jenner/Kardashian clan over her.

Blac Chyna’s dislike for the "Keeping Up With the Kardashians" star is no secret -- she even openly dissed Jenner on social media. She also posted texts she claimed she’d received from Tyga on April 23, telling her that he wanted to be a family again and raise their child together, according to Hollywood Life. Kylie and Tyga reportedly split after the incident but got back together shortly after.