Harry Styles is "in love" with Nadine Leopold.
The One Direction singer - who has previously dated TV presenter Caroline Flack and singer Taylor Swift - is said to be besotted with the Victoria's Secret beauty and she will be by his side at his 21st birthday party in Los Angeles on Sunday (01.02.15).
A source told The Sun newspaper: "Everyone's teasing him, saying he's in love, and he's not denying it.
"It's the real deal. He's never felt this way about anyone before.
"Harry has spent virtually all his free time in Los Angeles with Nadine.
"They're infatuated with each other and can't stand being apart.
"There's nobody else he'd rather be with on his birthday."
It was recently revealed the 'Steal My Girl' singer - who was first romantically linked with 21-year-old Nadine in November - "can't wait" for his birthday to come round because he is the only member of the band who as yet can't legally drink in the US.
A source said: "Harry can't wait to be able to legally drink in the US. He's in arguably the most famous pop band in the world but still can't get a drink in certain places.
"He's sick of being the butt of all the baby jokes in the group after being branded 'Baby Spice'."