Kat Armendariz, 27, captured the moment on June 29 just after 3 a.m. as her 20-year-old sister, Kimberly, was howling in pain while giving birth.
Kat, a mother of five, saw the humor in the situation and asked her kid sister for permission to take the now-viral snap.
“I told her, 'I am going to take this selfie and you can thank me later,'" Kat told Inside Edition. “I warned her that I wanted to take a selfie while she was in pain because I did my time already.”
“I wanted to capture that moment from the bottom of my heart. It was out of love," she said, but also, “I am her sister and a pain in the butt.”
Kimberly had been in labor for 15 hours inside Sierra Providence East Medical Center in El Paso before giving birth to her first child, a healthy baby boy named Zayden.
“I didn’t know what I was going to feel, but at that moment, she got it right on time,” Kimberly said of her sister's photo.
Kat said she's gotten “a lot of backlash” for the image from people online saying they would have never done that as their sibling was in pain but her sister didn’t mind at all.
“That is the relationship we have,” Kimberly said. “I was cool with it. I think it was funny!”
Kat then interjected, “I am her sister. I did my duty."