"It's been years of working on herself and getting better, but she's amazing—and a better singer, too, because she's healthy," he says.
Jonas -- who got his start on Disney alongside Cyrus, Selena Gomez, Joe Jonas, Kevin Jonas and Demi -- says there's definitely a "camaraderie" with the group.
"There's a camaraderie there, a sort of unspoken brother- and sisterhood.
Nick Jonas has had his fair share of hotties wrapped around his finger and has been romantically linked to even more girls before the Jonas Brothers became break out Disney Channel stars.
But, there's always one person he keeps coming back to and that is Demi Lovato.
However, let's take a trip down memory lane and check out all of Nick's ex-girlfriends.
We've found out why they broke up, a few tidbits about each of their relationships and why none of them compare to Demi.
It's a lot like watching your high school crush do well, just on a bigger scale." While the 23-year-old doesn't talk to Miley, his is still close with Demi -- they'll both be on the road together for their Future Now tour this summer.
Throughout their friendship, he's watched Demi -- who's been very vocal about managing her eating disorder -- grow and learn to love herself.
"I don't have a relationship with her now really, but that's not because we have any bad blood—we just sort of run in different circle," he says.
"It's pretty great, because I love 'Wrecking Ball' so much.
I still think it's one of the best pop songs of the last 10 years.