Melanie and Vanessa Iris Roy took the photos one year apart: First in January 2014 when Vanessa Iris was pregnant with their son Jax, and next in January 2015 while Melanie was carrying their daughter Ero.
The couple shared the combined photo on 13 February 2015, but the image only started to go viral two months later, after it appeared on several LGBT-focused sites - including a Brazilian advocacy group's Facebook page, where it reached over 150,000 likes.
"It's crazy to see that people were referring to my family as an inspiration. We are still in complete shock," Melanie told The Huffington Post.
"Vanessa and I have always said we would both like to carry.
"The woman's body is incredible. The way it creates and grows another human being is amazing.
"We hope that our picture is that sign that some women may need to encourage them to carry a child."
One Instagram comment that particularly touched Melanie came from Katirusia Eunoia:
"I am a heterosexual woman happily married to a man with two beautiful boys. The reason I even mention these facts is so you know that you not only touch the hearts and lives of gay couples, but you inspire EVERYONE."
Melanie replied: "Honestly its because of people like YOU that our world is continuously getting better. You are the brave soul here for taking the time to reach out to us. We appreciate you greatly!"
Vanessa Iris gave birth to Jax on March 18 2014 after six hours of labour in a birth centre.
Melanie gave birth to Ero on 18 February 2015, after an eight hour labour. She shared an incredible video of the water birth on Instagram with the following caption:
"Ero's birth. Well, how can i describe this... While it was the most painful experience I have ever went through, it was the most rewarding as well."
"The moment I looked down into the water and saw your head has made its way out, I no longer felt any pain. *Please be advised before pressing play*"