From the article: "Up to 600,000 civilians are still believed to remain in IS-held areas of Mosul.."
So it is your belief that all these civilians are ISIS family members ? I find that hard to believe given Mosul is not the only area held by ISIS and 600,000 people is a very large number. Even at 5 members per family, that's 120,000 fighters in Mosul alone. Consider what you are implying.
From 2015 : The terror group that calls itself the Islamic State "can muster between 20,000 and 31,500 fighters across Iraq and Syria," a CIA spokesman told CNN on Thursday."