My fiance's ex filed for child support against him She doesn't work and very rarely sees the children They also don't live with her will he have 2 pay

Child support is usually paid to the person who has the child in their care at least 50% of the time.  If mom does NOT have the child in her care, it's unusual for her to receive child support.  if you believe the child is being cared for by someone else, then you should take evidence of that with you to the support hearing.  keep in mind though, that dad may have to pay child support to whoever actually is the primary caretaker for the child.