Zuckerberg announced the news on his Facebook page, saying the couple feared they wouldn't be able to have another child given their difficulties conceiving Max.
'When Priscilla and I first found out she was pregnant again, our first hope was that the child would be healthy,' the billionaire said.
'My next hope was that it would be a girl. I cannot think of a greater gift than having a sister and I'm so happy Max and our new child will have each other.'
When the couple, both aged 32, announced their first pregnancy in December 2015, they revealed they had been trying to conceive for several years and that Priscilla had suffered three miscarriages before she fell pregnant with Max. So Zuckerberg still has time to do? Lol