Paracetamol and ibuprofen are different medicines that work in different ways, and in some situations a healthcare professional may suggest using them together or alternating them if a child is very uncomfortable and one alone is not helping. However, this should be done on advice, not by default, because it increases the chance of dosing mistakes.
The goal of fever medicine is comfort, not chasing a normal temperature. If your child is happy and drinking despite a fever, medicine may not be needed at all. Ibuprofen should be given with food and avoided in children who are dehydrated, have certain stomach or kidney conditions, or have chickenpox unless a doctor advises otherwise.
If you do use both, write down what you gave and when to avoid accidental double dosing, and keep each medicine within its own maximum daily limit. When in doubt, a pharmacist can give clear, child-specific advice.