Facebook CEO Mark Zuckerberg and Priscilla Chan announced the birth of their second daughter, August, on Monday.

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“Childhood is magical,” Zuckerberg wrote in a letter to his newborn daughter. “You only get to be a child once, so don’t spend it worrying too much about the future. You’ve got us for that, and we’ll do everything we possibly can to make sure the world is a better place for you and all children in your generation.”

August joins mom, dad, big sister Max and dog brother, Beast.

The couple announced their second pregnancy in a March Facebook post about family.

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“August, we love you so much and we’re so excited to go on this adventure with you,” Zuckerberg concluded the post with. “We wish you a life of joy, love and the same hope you give us.”