Geri Halliwell Horner Welcomes Son Montague George Hector

Ginger Spice has become Mama Spice for the second time!

Geri Halliwell Horner welcomed son Montague George Hector Horner at 8:48 a.m. on Saturday, Jan. 21, her rep confirms to PEOPLE. Baby Monty, as she and husband Christian Horner have nicknamed him, weighed in at 7 lbs., 8 oz. and joins big sisters Bluebell 10, and Olivia, 3.

The 44-year-old former Spice Girls member made the happy announcement on Twitter and Instagram on Saturday morning, sharing a photo of the newborn’s foot.

“Christian and I are delighted to announce our baby boy was born this morning weighing 7lbs 8oz ,” she wrote. “Montague George Hector Horner arrived this morning, a beautiful little brother for Bluebell and Olivia #amazing-day #grateful #monty”

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It’s Halliwell Horner’s first child with husband Christian Horner, although they each have daughters from previous relationships. The Horners — he a Formula 1 racing team boss — have been together since early 2014 and were married in England in May 2015 in a star-studded ceremony.

On Jan. 14, the “Look at Me” singer was surrounded by friends and family at her baby shower — hosted by longtime pal, interior designer Yassmin Ghandehari. Among the guests? Horner’s former Spice Girls bandmate Emma Bunton. Others sent their well wishes from afar, including Sporty Spice Mel C.

RELATED VIDEO: Geri Halliwell Horner Reunites with Fellow Spice Girl Emma Bunton – and Debuts Baby Bump!

Bunton has been by her friend Horner’s side multiple times during her pregnancy. In October, the duo stepped out together at the Attitude Awards 2016 in London, where Bunton presented Horner with the Honourary Gay Award — and Horner presented the world with the first glimpse at her adorable bump. And now, baby Montague and Bunton share a birthday — the Spice Girl turned 41 on Saturday.

The two are also reuniting with Melanie “Scary Spice”Brown, forming a new spinoff group GEM (a name made from the initials of their first names). Their first single, called “Song for Her,” leaked in November. The feel-good pop power anthem telling women who have lost their “careless and care-free” selves to the responsibilities of aging to “never forget the girl in the woman you are” — proving that the “Girl Power” spirit is still alive.

• With reporting by CYNTHIA SANZ