A GIRLFRIEND caught her man cheating with his own cousin after he forgot to switch off the tracking app on his phone.

Milli Hansen, 20, said her “world fell apart” when she saw partner Stan Stockton-Price in a steamy embrace with cousin, The Sun reports.

Stan, 24, from Grimsby, England had reportedly set up the tracking app to bring the couple closer together while he worked away at sea.

But his affair was revealed when he sneaked out to romp with his cousin while Milli babysat his little sister.

Stan was supposed to be out at the local town hall celebrating his aunty’s 50th birthday, but as the night went on Milli became concerned when she heard nothing from him.

After a while she checked the tracking app on her phone and sat-nav led her to Stan’s aunty’s home.

Milli told the Mirror: “I looked through the window and all I could see was Stan’s clothes strewn over the floor.

“Then I caught sight of his cousin topless — with Stan beneath her. I felt sick.”

Milli banged on the door and her boyfriend’s cousin arrived wearing a dressing gown with a shamefaced Stan cowering behind her.

Furious, she called her boyfriend’s mum before racing home, devastated.

Milli has vowed never to “trust a man again” after the heartbreak.

Stan said he felt guilty about cheating on his girlfriend.

“Of course I feel bad, but I can’t change what’s gone on. One thing just lead to another and things just escalated,” he said.