Kelly Osborne and Matthew at the Victoria & Albert Museum on October 30, 2012 in London. Credit: Dave J Hogan/Getty Images

Kelly Osbourne has found a keeper in boyfriend of more than a year Matthew Mosshart -- and her famously close-knit clan agrees.

"Kelly's family loves her boyfriend," a source tells Us Weekly. "They think he's the nicest guy she's ever dated. He is very patient and down-to-earth."

Indeed, the vegan chef, 29, who moved cross-country from NYC to be with Osbourne in L.A., is helping the outspoken E! host, 28, learn to relax.

"She tends to be kind of a diva," explains a pal. "So his sweet nature is good for her."

And it shows.

The pal adds, "Kelly is the happiest she's ever been. Her career is going well, and she's in a healthy relationship with a wonderful guy."