Beyonce and Jay Z’s twins arrived ahead of time.
The babies were born prematurely and are being treated for jaundice, TMZ has reported.
The pair have not left the hospital since arriving eight days ago; it was previously reported doctors had opted to keep them in for a ‘minor issue.’
The siblings will have spent most of their first days under ‘bili lights,’ phototherapy designed to eliminate high levels of bilirubin in the blood.
Jaundice is quite common among newborns, especially preterm births; twins are more susceptible since they are rarely carried to full term.
The yellow substance is created when old red blood cells are replaced by new ones; heightened levels cause a baby’s skin and eyes to turn yellow.
Untreated it can be very dangerous, but once diagnosed it is easily and usually successfully treated.
On Sunday Beyonce’s dad Mathew Knowles confirmed via Twitter the couple had added two more members to the family, joining five-year-old Blue Ivy.
News that the singer had given birth the day before ignited social media, with the Bey hive fan group buzzing over the yet unrevealed s3xes and names of the latest members of the Carter Clan.
‘They’re here! #beyonce #twins #jayz #happybirthday,’ Mathew Knowles wrote on Twitter, posting a card saying: ‘Happy birthday to the twins! Love, Granddad.’
There was no such comment from Beyonce or Jay Z, who grew up as Shawn Carter.
Speculation grew when an unidentified woman was photographed Friday carrying a large bouquet of pink, blue and purple flowers – complete with a card that appeared to read ‘B + J’ – along with twin pink and blue balloons in the shape of feet that read ‘Baby Girl’ and ‘Baby Boy.’
Beyonce revealed in February that she was expecting, commanding the internet by posting a picture of herself kneeling beside a human-size floral arrangement, her hands cradling her rounded belly.
‘We would like to share our love and happiness. We have been blessed two times over,’ the 35-year-old singer wrote.
Speculation that her due date had approached was fueled earlier this week when Jay Z, 47, was absent at the Songwriters Hall of Fame.
The rapper took to Twitter to thank artists who had influenced him as well as former US president Barack Obama.
Obama hailed the hip-hop mogul – who campaigned actively with Beyonce for the first African American president – as a kindred spirit at the event in a surprise appearance by video.
‘Jay and I are also fools for our daughters, although he’s going to have me beat once those twins show up,’ the former president and father of two joked.
Some fans clamoring for details on the twins took Obama’s aside as a hint that the babies might be girls.
But no concrete details regarding s3xes or names of the babies have been revealed.
Beyonce and Jay Z are among the most commercially successful figures in music, with a combined net worth estimated at $1 billion.
In the aftermath of news that the twins had arrived the rapper’s music streaming service Tidal announced early Monday that Jay Z was set to drop a new album titled ‘4:44’ on June 30, confirming weeks of rumors.