Foreign Service children become adults at age 18 in the United States. It is important, as the parent of a child in the Foreign Service, to know at what age some of the regulations change. Employees should contact their Career Development Officer (CDO) regarding their child(ren) being on orders. Also please note that at 21 there may be some age restrictions for Foreign Service children.  /www.state.gov/m/dghr/flo/c21961.htm