bfb3a285_SSA_Handbook___211__If_the_worker___
A dependent, unmarried child of a deceased worker if the child is: (A) Under 18; (B) Under 19 and a full-time elementary or secondary school student; or (C) Age 18 or over and under a disability which began before the child reached age 22. [If the worker...] 
Is either fully or currently insured.
SSA Handbook § 211
If the worker...