One Twitter user was quick to point out that the current photo was similar to one used last year but with roles reversed.
The mother of both girls took to Twitter to explain that they are adoptive sisters.
Gap told Fortune, "As a brand with a proud 46-year history of championing diversity and inclusivity, we appreciate the conversation that has taken place and are sorry to anyone we've offended."
>> Read more trending stories
The company plans to remove the offending image.
The advertising campaign promotes GapKids X ED, which is Ellen DeGeneres' line for Gap.