She signed the pic, "The Carters," using her husband Jay Z's real last name.
Beyonce and Jay Z are already parents to daughter Blue Ivy, born in 2012.
In 2013, Beyonce spoke to ABC News and told Amy Robach that she definitely "would like more children."
"I think my daughter needs some company. I definitely love being a big sister," she added of little sister Solange Knowles. She added in that interview that she's "very protective" of her daughter Blue Ivy.
"I just want to make sure that she can have a healthy, safe, normal life … in the back of my mind, she's my priority. And life is completely different now. So I'm -- I feel really, really just lucky that I can still do what I love, and now have a way bigger meaning. And that's to be her mother," she said.
ABC News has reached out to Beyonce for comment.