The National Genealogical Society uses a variation of the Register System in its publication, the National Genealogical Society Quarterly (NGSQ). Although the two systems may seem alike, there are numerous differences. The NGSQ System assigns numbers to all children in each family, whether or not they have documented descendants. A plus symbol prior to the number is used to indicate if the line is later carried on.
For an up-to-date guide to the NGSQ System, readers should see Numbering Your Genealogy: Basic Systems, Complex Families, and International Kin, published by the National Genealogical Society. It also describes numbering for adoptions, cousin marriages, stepkin and more complex family relationships.