DoD Knowledge Base: FAQs
Yes. "Only sons" or "the last son to carry the family name," and "sole surviving sons" must register with the Selective Service and they can be drafted. However, individuals may be entitled to a peacetime deferment if there is a military death in the immediate family.
Provisions regarding the survivors of veterans were written into Selective Service law after World War II. Details have varied over the years, but the basic premise remains the same: where a family member has been lost as a result of military service, the remaining family members should be protected as much as possible. It is important to keep in mind that the provisions are directly related to Service-Connected Deaths. The "only child" or "only son" does not qualify him for consideration to these provisions - he must be the survivor of someone who died as a result of military service.
For more information on this provision, or other facts about military service exemptions, contact the Selective Service System at: http://www.sss.gov/default.htm.