Kendall Jenner growing closer to Devin Booker: 'Everyone Is Rooting for Them'

Kendall Jenner's romance is getting serious with boyfriend Devin Booker as she grows closer to him.

As revealed by a source, the supermodel 'is crazy' about her beau and everyone around them is 'rooting for them.'

"She is crazy about him. She has never looked happier. Her whole family loves Devin too," a source tells PEOPLE about the couple, who recently marked their first anniversary.

"Devin is such a cool guy. He is very low-key and doesn't want to be a celebrity. He is very sweet to Kendall," the insider added.

They went on to add that things got serious between the duo last summer.

"They got serious quickly last summer. Kendall visited him a lot in Phoenix. After Devin finished the season, he stayed with Kendall in LA," the source said.

Added the source: "They spent the whole summer together and even vacationed with Justin [Bieber] and Hailey [Baldwin Bieber]. They're still young, but everyone is rooting for them. They are a great couple."