Mark Zuckerberg celebrates National Sibling Day with throwback photo of himself with his three sisters

Yesterday was National Sibling Day in America
and celebrities took to social media to post old
and new photos of themselves and their
brothers and sisters. Facebook CEO Mark
Zuckerberg shared a photo of himself and his
siblings as kids from the 1980s. "Happy Sibling
Day to my three wonderful sisters. Here we are
having a great time and rocking our awesome
1980s ski jackets." he captioned the photo