The stars revealed their pregnancies earlier this year and were thought to be due around the same time, but Pinnock has now told fans that she has had twins - and they arrived earlier this month.
Sharing a sweet photo on Instagram of her newborns' tiny feet being cradled by two hands, she wrote: "We asked for a miracle, we were given two... Our Cubbies are here 16/08/21"
The babies arrived five days before Edwards gave birth on Saturday, and she made her own birth announcement yesterday as she posted: "Welcome to the world baby 21/08/21"
Pinnock and Edwards had managed to surprise fans with their baby news by keeping their bumps under loose-fitting clothes until just a few months ago, but it seems Pinnock was hiding an extra secret as she was expecting twins.
The 29-year-old singer has become a first-time parent with footballer fiance Andre Gray, while her 28-year-old bandmate Edwards welcomed her first child with footballer Alex Oxlade-Chamberlain.
Stunned fans commented on Pinnock's post with one saying: "Oh my goodness! Twins the biggest congratulations Leigh"
Another fan wrote: "Wait?? TTTTWWWWIINNSS???"
Someone else added: "Two! Amazing"
Little Mix formed on The X Factor in 2011 and have become one of the country’s biggest-selling girl bands since winning the series.
They left Simon Cowell’s Syco Music for the RCA label in November 2018 and became a three in December when Jesy Nelson left the group, saying the high-profile role had “taken a toll” on her mental health.
Pinnock, Edwards and bandmate Jade Thirlwall became the first girl group to win best British group at the Brits earlier this year, shortly after they announced their pregnancies.
Watch: Little Mix congratulate Perrie Edwards on giving birth