Kelly Osbourne Shows Off Baby Bump At Sister-In-Law's Baby Shower

Baby fever is at an all-time high in the Osbourne family ... as Kelly Osbourne showed off her baby bump while attending a baby shower for another family member.

Kelly was all smiles as celebrated her brother Jack and his fiancée, Aree Gearhart, at their baby shower -- held at Ozzy and Sharon's house. Jack and Aree are expecting their first child together.

Of course, Kelly was on auntie AND soon-to-be-mommy duty ... she rocked a light pink dress and violet hair, but her growing baby bump stole the show. As we've reported, Kelly announced she was pregnant for the first time earlier this month.

She wrote on Instagram, "I know that I have been very quiet these past few months so I thought I would share with you all as to why… I am over the moon to announce that I am going to be a Mumma..."

While she didn't say who she was having a baby with, she recently told her followers she was dating Sid Wilson from "Slipknot" when she wrote, "after 23 years of friendship I can’t believe where we have ended up! You are my best friend, my soulmate and I am so deeply in love with you Sidney George Wilson."