PHOENIX — Amberkatherine DeCory carried photos of her daughter’s birth certificate in her diaper bag in case she had to prove that the lighter-skinned girl was really hers.

Cydnee Rafferty gives her husband a letter explaining that he has permission to travel with their 5-year-old biracial daughter.

Families like theirs were not surprised when they heard that Cindy McCain had reported a woman to police for possible human trafficking because the widow of Sen. John McCain saw her at the airport with a toddler of a different ethnicity. Officers investigated and found no evidence of wrongdoing.

Parents whose children have a different complexion say they regularly face suspicion and the assumption that they must be watching someone’s kids.

“This is a problem that, to be frank, well-meaning white people get themselves into,” said Rafferty, who is African-American and whose husband is white.

After McCain’s report, Rafferty posted a selfie on Twitter of her with her two children, ages 5 and 5 months. “I know they don’t look like me, but I assure you, I grew them in my belly,” she wrote to McCain.

Earlier this month, McCain claimed on Phoenix radio station KTAR that the woman was waiting for a man who bought the child and that her Jan. 30 report to police had stopped the trafficking.

“I came in from a trip I’d been on,” McCain said. “I spotted — it looked odd — it was a woman of a different ethnicity than the child, this little toddler she had. Something didn’t click with me. I tell people ‘trust your gut.’?”

Phoenix Police Sgt. Armando Carbajal confirmed that McCain requested a welfare check on a child at the airport, but said officers found “no evidence of criminal conduct or child endangerment.”

A spokesman for the McCain Institute for International Leadership at Arizona State University said McCain was “only thinking about the possible ramifications of a criminal act, not the ethnicity of the possible trafficker.”

Rafferty, a 38-year-old New Yorker, was surprised that McCain, who adopted a daughter from Bangladesh, would make the same something’s-not-right assumption that mixed-race families grapple with constantly. It’s not always summoning the police. Other, more common ways of calling out the differences sting too.

For Rafferty, the questions are offensive: “Whose baby is that?” from a woman in the grocery store. “You’re the ?” followed by a pause for her to fill in the blank with “mom.”

And if she pushes a stroller on Manhattan’s Upper West Side, everyone assumes she’s the nanny.

DeCory, 38, a police officer outside Minneapolis who has African-American and Native American ancestry, said the anxiety between mom and baby is a constant challenge for mixed-race families that isn’t talked about enough.

Until her daughter, Mila, could speak, DeCory carried her birth certificate and a photo of her giving birth, just in case she had to prove that her light-haired, blue-eyed child was her own. “I would get anxiety going out with her in public,” she said. “I was very reluctant to breastfeed her in public or do anything that would draw attention to me.”

Mila is now 11 and her hair has darkened.