Allah (SWT) knows the future of every one, and He has The Absolute Wisdom and Absolute Mercy. He ordains (when and how and where should be) the birth of every human being . No one will face any injustice because of others. Allah's Mercy is on and for all and every one will enjoy Allah's Mercy and Justice. Those who were born in Non Muslim families will never be punished because of that, but will be given plenty of chances to know the truth and full ability to decide and follow.