"Islamophobic" math based on Human Rightsphobic islam
Of these "coming alone child-refugees" most are muslims. 90% are teenage boys and most of these are late teenage youngsters.
According to islam a child fathered by a muslim is always a muslim no matter who the mother is.
So it's not only that muslim mothers have many more children than non-muslim Europeans - non-muslim mothers having children with muslim men inevitably loose their children to islam.
So what to do?
Simple. Most muslims have a brain and understand logic. So face them with Human Rights logic according to which their system is racist and sexist. Most of these young males will probably abandon sharia islam if seriously challenged at all societal levels with the illogic of this supremacist ideology. And those who don't, then clearly define themselves as hateful and racist supremacists.