I have bee diagnosed with tb, my twins are 5year and 3months old. we are taking them for x-rays tomorrow. if their lungs are clear should they still receive preventative medication?

Probably yes: The care plan for members of the family depend on the particular details in that case and on the local TB prevention guidelines. In the US, if a young child has been living with a TB-infected caretaker, the child is presumed exposed. If the child has no symptoms and has a normal chest x-ray, that child probably will receive preventive treatment for 9 months (sometimes 6 months).