Among babies, flat heads aren't uncommon: Half of all infants may develop "flat-head syndrome," in which babies' heads become misshapen from all that time spent on their backs.
Babies wearing corrective helmets to treat the condition isn't rare, either. But a whole family wearing helmets in solidarity? That's adorable enough to go viral.
When 4-month-old Jonas Gutierrez started wearing his helmet last week in San Antonio, his 3-year-old sister, Camila, wanted one so her brother wouldn't "feel different," as TV station KENS reported.
Soon, the whole family had head gear, and photos of them spread across the web.
"I love that Camila can be exposed to something valuable like inclusion for those who are 'different,'" the siblings' mother, Shayna Gutierrez, said.
"But the truth is we were just being our normal selves on a normal Saturday morning at home, and just give in to the requests of our 3-year-old who asks us to wear helmets."
Baby Jonas isn't old enough to appreciate the gesture, Shayna said, but it's made for some sweet sibling bonding.
After a cousin of the family posted a photo of the kids and their dad, Gary Gutierrez, on Twitter, it received 27,000 retweets. Many replied with photos of their own helmet-clad kids.
Jonas has taken to his headwear just fine, minus the sometimes smelly sweat it causes under the hot Texas sun, his mother said.
He'll wear the helmet for two to six months, KENS-TV reported, and the family is excited about his progress.
The Gutierrezes realized Jonas had a "severe case" of brachycephaly, a form of flat-head syndrome, after a four-month check-up, Shayna said. The child's head had grown so rapidly that it began affecting the shape of his face, she recalled.
Jonas' solid sleeping habits didn't help his condition, his mother explained: "He has great muscle control and does his recommended tummy time, but he just always settled on that spot and slept with his head right on it."
"At first I felt a bit guilty but I got over that quickly," Shayna said, adding: "We thank God for two healthy kids and for fun time spent together as a family."
Follow Josh Hafner on Twitter: @joshhafner