Table 1. Pedigree relationships (R), Wright’s coefficient of relationship (R), and abbreviations used.

Relationship R	Full-sib family-based R		Half-sib family-based R		Lineal R
1/4	Uncle–nephewa	UN	Half-sibs	HS	Grandparent–grandoffspring	GPO
1/8	Great-uncle–great-nephew	GUGN	Half-uncle–nephew	HUN	Great-grandparent–great-grandoffspring	GGPO
1/8	Full cousins	C
1/16	Cousins once removed	C1R	Half-cousins	HC	GtGtgrandparent–	G3PO
					GtGtgrandoffspring
1/16			Half-great-uncle–great-nephewb
1/32	Second cousins	2C	Half-cousins once removed	HC1R	GtGtGtgrandparent–	G4PO
					GtGtGtgrandoffspring
1/64	Second cousins once removed	2C1R	Half second cousins	H2C	Further generation as above	G5PO
1/128	Third cousins	3C	Half second cousins once removed	H2C1R	Further generation as above	G6PO

UN, uncle–nephew; HS, half-sib; GPO, grandparent–grandoffspring; GUGN, great-uncle–great-nephew; HUN, half-uncle–nephew; GGPO, great-grandparent–great-grandoffspring; C, cousin; C1R, cousin once removed; HC, half-cousin; Gt, great; G3PO, great-great-grandparent–great-great-grandoffspring; 2C, second cousin; HC1R, half-cousin once removed; G4PO, great-great-great-grandparent–great-great-great-grandoffspring; 2C1R, second cousin once removed; H2C, half second cousin; G5PO, great-great-great-great-grandparent–great-great-great-great-grandoffspring; 3C, third cousin; H2C1R, half second cousin once removed; G6PO, great-great-great-great-great-grandparent–great-great-great-great-great-grandoffspring.

^aIncluding uncle/aunt–nephew/niece.

^bRelationship not included in subsequent Tables as the distribution is identical to that for half-cousins.

Similarly, other relationships with the same R and family base but different pedigree are not analyzed, e.g., (full) cousins twice removed ≡ second cousins (R = 1/32), and half-cousins twice removed ≡ half second cousins (R = 1/64).