Well, it is a part of fighting the terrorism, sadly - there have been two or three cases where the terrorist that struck in Paris and in Brussels have passed themselves as refugees/asylum seekers and their track has been lost because of poor documentation.
Then there has been the recent case of the active duty (!) German soldier that has managed to pass himself for a refugee, including obtaining accommodation in a refugee center and applying for an asylum under a fake identity. He then planted some fake letters with islamist threats and a bomb that has damaged the bus of a German soccer team, with the idea being to frame the migrants/refugees for it. It was a huge scandal.
None of these were children but the common thing was the chaos in the documentation and evidence permitting this to happen.
