Justin Bieber's new sister

Justin Bieber has a new baby sister.

The 'Love Yourself' hitmaker was proud to show his fans a glimpse of little Bay - who was born to his father, Jeremy Bieber, and step-mother Chelsey on Thursday (16.08.18) - 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.

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)"

Meanwhile, the 'Believe' hitmaker - who is engaged to Hailey Baldwin - previously defended his father against accusations he was a "deadbeat dad" when the pop superstar was growing up.

He said: "He was immature. He left for like a year when I was about four, went to British Columbia, came back on Father's Day.

"I remember my mom said, 'If you're going to be here, you have to be here'. There's a misconception that he's this deadbeat dad, but he has been in my life since. I was with him on weekends and Wednesdays."