Kelly Osbourne believes her brother Jack will be the "best dad in the world."

Jack announced in October that he is expecting his first child with fiance Lisa Stelly.

Kelly is convinced that Jack will be an incredible father to his new baby.

"He's going to be the best dad in the world," Kelly told E! Online.

"Not a lot of people know this about my brother, but this is what my brother has wanted for a really, really long time."

Jack and Kelly are the children of Black Sabbath star Ozzy Osbourne and America's Got Talent judge Sharon Osbourne.

Although the Osbournes are a loving family, Kelly thinks that Jack is insistent on setting a better example for his child than his dad Ozzy who battled with drink and drug problems - did for him.

"It's no secret, growing up we didn't have the world's greatest father," Kelly explained. "We had the most loving father, who then turned into the best father in the entire world, but there was a time when he wasn't. And I think for Jack... he wants to make a family, and he wants to be the best dad in the world."

Kelly is elated that her brother is happily in love.

"It couldn't have happened in a better way," she gushed.

"[Jack] met the most amazing girl, they fell in love, they're getting married and they're having a baby. It's like a fairy tale."

With the holiday season coming up, Kelly will purchase gifts for her whole family, including her unborn niece or nephew.

"Lisa gets her gift, Jack gets his gift and, even though the baby's not born yet, the baby's getting their gift, too."

Jack rose to fame in the family's reality show The Osbournes.

He and Lisa are expecting their baby in 2012.