Harry Styles is allegedly cheating on girlfriend Kendall Jenner.

The young couple have only been dating for a couple of months but Harry is already rumoured to be cheating on the pretty model.

The One Direction singer is reportedly seeing 29-year-old Haley Grialdo, daughter of Eighties rocker Pat Benatar, and has been on and off since last year.

According to a source close to the star, his relationship with Kendall, 18, has not affected this.

“They met in Los Angeles last year at a One Direction concert and have seen each other on the sly anytime Harry’s been back in town,” the source told British Star magazine.

“They talk almost every day when he’s in London and he sends her lots of romantic gifts. They've been trying to keep it on the down-low.”

Harry, 20, started dating Kendall, who is the half-sister of reality star Kim Kardashian, back in November.

A close friend of Kendall insists she will be devastated to discover the news of Harry and Haley as she is head over heels for the heartthrob.

“She really loves Harry and had opened herself up to him. It hurts to find out they weren’t exclusive like she thought.”

Despite the allegations, it has been reported that Harry chose to spend his recent birthday with Kendall at her father Bruce Jenner’s house in Malibu instead of flying home to the UK.

A source told British newspaper The Sunday People, “Kendall was really keen to make Harry’s birthday a memorable one. Her dad Bruce owns an incredible clifftop holiday home in California which has amazing views.

“The secluded house is perfect for them to spend quality time together. It’s also ideal for a party with Kendall’s sisters.”