The other week border officials at Eurostar's UK Passport Control in Brussels asked me to prove my daughter was in fact my daughter. They said they were challenging me because we do not share a surname. Here's an article for The Guardian that I have written about this, published today.
Travel troubles: the problems of not sharing your child's surname
And here are articles about the Mexican case to which I refer:
The blond 'Mexican beggar child' story holds a mirror to US perceptions of race
Little blonde beggar girl whose treatment has sparked race row in Mexico
And a previous post by me on a similar subject:
I did not steal my baby