does an individual have to pay Child Support when the Ex- and the Children are living together?

It depends on the state. In most states if all parties live together then the child support is dropped. You will need to file a modification of child support with the clerk of the circuit court. Check with free family legal aid at your courthouse they can walk you through the paper work. Hope this helps

I'm not sure I understand your question. If you are legally the non-custodial parent having to pay child support and now the children are living with you, then you need to go to court to have the child support amended. It doesn't happen automatically.

Sure do if any of those kids are biologically yours or you adopted any of them, as who shes living with has no bearing on child support, but may if its an endangering or hostile environment to the kids but thats another thing so it all comes down to if youre the legal father to any of the kids here

As in - you and your ex are co-habitating with the children so you are covering expenses at this time? If co-habitating and sharing expenses - no to the child support.

I'm not sure but you should man up and offer to pay it with or without the law telling you too. You have one wage to cover one person, she has one wage to cover two or more and since they are you're kids anyway.