Justin Bieber has an adorable new baby sister!

Justin Bieber already has a cute wee brother and now there's a new addition to his family as his step-mother has just given birth to has a new baby sister!

Biebz was proud to show his fans a glimpse of the little girl - who was born to his father, Jeremy Bieber, and step-mother Chelsey on his Instagram account just hours after she was born.

Alongside the photo, he posted: "Meet the newest bieber, my little sister BAY BIEBER.(sic)"

Jeremy - who has Justin with Pattie Mallette and two other children, Jazmyn, nine, and eight-year-old Jaxon from his marriage to Erin Wagner - also shared a photo of his new baby with his 30-year-old wife from the delivery room.

Smiling in the photo, he wrote on Instagram: "We welcomed a healthy baby "Bay Bieber" born at 830 am (sic)".

Jeremy, 43, married Chelsey in a pink-themed wedding in Jamaica in February - which was attended by his famous son and his then-girlfriend Selena Gomez - and announced her pregnancy just a few days afterwards.

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He shared a photo on Instagram of Chelsey showing off her growing bump in a floral bikini and captioned the post: "My beautiful wife and... (sic)"