Meet the baby Carters.

Beyoncé and her husband Jay-Z have welcomed two new tiny members into their family. The genders of the twins aren’t known yet, but Beyoncé’s dad, Matthew Knowles, announced the news in a tweet in which he wrote “They’re here! Happy Birthday to the Twins!” The infants will join Blue Ivy Carter, the couple’s five year old daughter, who starred in a Sandro Botticelli-inspired photoshoot with her visibly pregnant mom.

Queen Bey and Jay-Z are not the only mega stars who’ve had recent double bundles of joy: Amal and George Clooney recently gave birth to a pair of twins.

Good thing these couples are loaded: According to a 2013 study published in the American Journal of Obstetrics & Gynecology, having twins isn’t just double the trouble. The medical costs of conceiving twins is $105,000, or quintuple that of single births. (Having triplets is 20 times as expensive.)

Of course, George and Amal and Beyoncé and Jay-Z will likely pay way more than $105,000. Knowles gave birth to Blue Ivy in a ritzy section of New York City’s Lenox Hill Hospital, where $17,000 per night rooms are reportedly equipped with plush robes and multiple plasma screens.

Also read: ‘Property Brothers’ Talk Dream Homes and Technologies

While the costs of buying baby formula and diapers simply double, it’s the medical bills that mount exponentially. That’s because of the risks of delivering multiple babies. According to the researchers behind the journal article, mothers and their multiple pregnancy infants suffer from higher mortality rates — although the absolute number of maternity-related deaths in the U.S. is still low. They also tend to require extended stays in hospital, are more susceptible to illness and caesarean sections are used more often.

Aside from health care, having multiple babies at once also eliminates the possibility of using hand-me-downs. However, in Beyoncé’s case, if the twins follow in the footsteps of Blue Ivy—who has appeared in music videos and walked red carpets—fashion designers will be flocking to dress them in branded baby bibs. They’ll have a running head start: Beyoncé’s post disclosing her pregnancy has swiftly become the most liked photo on Instagram.

Americans across the board are having more multiple conceptions. According to the Centers for Disease Control and Prevention, twin birth rates spiked to 33.9 per 1,000 births in 2014, up more than 75% from 1980. That’s partly due to older mothers: those 35 and above are more likely to have twins. Doctors say this is because of growing use of fertility treatments.

This story was originally published on MarketWatch.

This story was updated on June 19 2017 with news of the birth of Beyoncé and Jay-Z’s twins. 

This story was updated on June 6 2017 with news of the birth of Alexander and Ella Clooney.