Kelly Osbourne Reveals Her Closest Confidant During Pregnancy -- And the Answer May Surprise You (Exclusive)

Tune in to Tuesday's episode of Entertainment Tonight for more of our interview with Kelly Osbourne.

Kelly Osbourne is preparing for parenthood.

The reality star will be welcoming her first child in the coming weeks and, in a new interview with ET, is revealing who has been her biggest supporter during pregnancy. But it's not who you might think!

While Kelly's boyfriend, Slipknot DJ Sid Wilson, has been away on tour, she says she's leaned on her brother, Jack Osbourne, throughout much of her journey toward motherhood. 

"He's actually my biggest confidant," she tells ET's Matt Cohen. "My first phone calls every single day." 

Jack welcomed his fourth daughter, Maple Artemis Osbourne, in July. While Maple is his first child with fiancée Aree Gearhart, Jack also shares daughters Pearl, 10, Andy, 7, and Minnie, 4, with his ex-wife, Lisa Stelly.

"I check in on baby Maple and they check in on me to see where I am -- and they were pregnant the same time, she just came a few months earlier, so it’s kind of like he's been my crash test dummy," Kelly jokes. 

"Everything that he's doing, I'm like, 'OK, how do you do that?' and, 'That's how you burp the baby?'" she admits with a laugh. "I feel clueless, I really do. But I feel like once everything happens, it will become like second nature. But it has been a great help." 

Kelly says that she's even taking some childcare practice runs with her new niece. 

"He came over yesterday and he was like, 'OK, your turn.' And I get to play with Maple," she says. 

"It's amazing that it is the fourth one and the fourth girl," she adds. "I'm always like, 'Ah ha, Jack, you had four girls. That's what you get!' But he's the best dad and he's so hands on with them. ... If I'm half as good a parent as my brother is, I will be great." 

Kelly also gushes over her tightknit relationship with her own father, rock legend Ozzy Osbourne, amid her pregnancy. 

"My parents have been incredible and been with me every step of the way on this journey, 'cause my boyfriend is in a band, they tour, so, he's hardly been here, so, every milestone I've kinda gone through with my dad, and he's been great," she gushes. "Even though he sometimes says the wrong thing. I'll walk into the room and he'll go, 'Wow, you're big.' and I'm like, 'Thanks, Dad.'"

Kelly also confirms with ET that she is, in fact, expecting a baby boy, after her dad publicly spilled the beans. 

"I mean, he's told everyone," Kelly says, "....the gender of my baby before I ever got the chance to, and I'm just like, 'Aww Dad, come on. Like, come on,' but I will say, every single day he does this little song and this little dance about how excited he is, and he is so excited that it's a boy. It's the first -- out of me and my brother, it's the first boy, so, he's like planning all these things."

But Kelly admits she's already had to set some grandparent boundaries.

"He wants to buy, like, 'We're gonna get him air rifles,'" she says of Ozzy's plans, "and I'm like, 'No, you're not. No, you're not. Absolutely not!'" 

Their father-daughter dynamic will undoubtedly be highlighted on her parents' new show in the U.K., Home to Roost. Kelly reveals to ET that she's already involved in the project, which will show how she and boyfriend Sid -- who is half English -- split their time between the U.S. and the U.K. with their new child. 

"I'm doing the show too," she announces. "It's weird, at first I was like, 'Oh, am I going to get PTSD? Is this strange?' But the more we're kinda getting in the swing of it, it's just like second nature. I mean, I get paid to be myself, so, it's great."

Tune in to Tuesday's episode of Entertainment Tonight for more of ET's interview with Kelly.

She is also shedding light on No Sugar Day, which fell on Oct. 3. No Sugar Day is an international initiative championed by Brad Woodgate to get people and other food companies to make the conscious decision to decrease their sugar intake for a healthier mind and body.

The initiative is especially important for Kelly, who revealed she was diagnosed with gestational diabetes in her third trimester of pregnancy. 

"I had terrible terrible, terrible heartburn, acid reflux, my feet were swelling, and I was having rapid weight gain, and I was like, 'I don't understand this, I'm not eating enough to make this add up, what's happening?''' Kelly says of the symptoms that led her to believe something was amiss.

"So, I went to the doctor, and I'd already done a test and passed it, but then when I got to my third trimester, they tested me again and it turned out that I had gestational diabetes, and the whole time, I just sat there being like, 'What what did I do wrong? What am I eating that's so bad?' Because I thought I was eating relatively healthy," she continues. "It turns out, I was not, but it was not anything I did. You either get it, or you don't, and I think it's more to do with me being 37 than any amount of sugar that I was eating. But now that I know what I know about sugar, I don't think I'll ever eat the same again."