"They're here! #beyonce #twins #jayz #happybirthday," Mathew shared the news along with a photo of balloons and a message, "Happy Birthday to the twins ! Love, Granddad."
Although there has been no official announcement about the babies gender, reports suggest that the Lemonade singer gave birth to a boy and a girl. US Weekly quoting multiple sources close to the richest couple reported, "Blue Ivy has a new little brother and sister."
A source close to the couple confirmed to PEOPLE that the Carter family is thrilled to welcome the newest members. "Bey and Jay are thrilled and have started sharing the news with their family and closest friends," the source said.
Beyonce and Jay Z, who married in 2008, are parents to a five-year-old daughter, Blue Ivy. The singer had made the announcement about her second pregnancy in February. Beyonce shared her baby bump photo and captioned it, "We would like to share our love and happiness. We have been blessed two times over. We are incredibly grateful that our family will be growing by two, and we thank you for your well wishes."
Meanwhile, fans of the Carter family wished the couple on Twitter and also said that they want the photos of the newborn.
"Congrats to Beyoncé, leading the matriarchy by deliberately stealing the spotlight on a day devoted to men. #beyoncetwins," a fan tweeted.
"Congrats #beyoncetwins all my best wishes for a long happy life xoxo," Twitter user said.
"STOP EVERYTHING RIGHT NOW! @Beyonce had the twins!!? I need names people! Names!! #beyoncetwins."
"I am not ready for the day @Beyonce posts a twin picture out of no where. #beyoncetwins."