Table 2.

Distributions of Nuclear Families of Various Sibship Sizes, in the All-Ages Sib-Pair Sample and in the Sample of Sib Pairs <18 Years of Age

	No. of Nuclear Families in Samples of Sibships of
Sibship Size	All Ages	Age <18 Yearsa
Two sibs	37	32
Three sibs	25	29
Four sibs	13	6
Five sibs	3	1
Seven sibs	1	0
Total	79	68

^aRestriction to sibs <18 years of age resulted in the exclusion of 11 nuclear families; therefore, the total number of nuclear families in this sample was 68, and the distribution of sibship sizes in the remaining nuclear families changed.