You cannot be born a muslim or any other religion for that matter. It is knowledge that has to be acquired, and when you pop out of the womb you cannot do that.
A child has no say on how it is brought up, so if it is taught one religion, be it islam or christianity, then there is nothing it can do about it.
When the child reaches adulthood, then it is free to either believe what it has been taught, or follow another path.
You'll be telling us Boris Johnson is muslim next because his Grandfather was.